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Diffstat (limited to 'rts/GC.c')
| -rw-r--r-- | rts/GC.c | 4719 |
1 files changed, 4719 insertions, 0 deletions
diff --git a/rts/GC.c b/rts/GC.c new file mode 100644 index 0000000000..a13cd33afa --- /dev/null +++ b/rts/GC.c @@ -0,0 +1,4719 @@ +/* ----------------------------------------------------------------------------- + * + * (c) The GHC Team 1998-2003 + * + * Generational garbage collector + * + * ---------------------------------------------------------------------------*/ + +#include "PosixSource.h" +#include "Rts.h" +#include "RtsFlags.h" +#include "RtsUtils.h" +#include "Apply.h" +#include "OSThreads.h" +#include "Storage.h" +#include "LdvProfile.h" +#include "Updates.h" +#include "Stats.h" +#include "Schedule.h" +#include "Sanity.h" +#include "BlockAlloc.h" +#include "MBlock.h" +#include "ProfHeap.h" +#include "SchedAPI.h" +#include "Weak.h" +#include "Prelude.h" +#include "ParTicky.h" // ToDo: move into Rts.h +#include "GCCompact.h" +#include "RtsSignals.h" +#include "STM.h" +#if defined(GRAN) || defined(PAR) +# include "GranSimRts.h" +# include "ParallelRts.h" +# include "FetchMe.h" +# if defined(DEBUG) +# include "Printer.h" +# include "ParallelDebug.h" +# endif +#endif +#include "HsFFI.h" +#include "Linker.h" +#if defined(RTS_GTK_FRONTPANEL) +#include "FrontPanel.h" +#endif + +#include "RetainerProfile.h" + +#include <string.h> + +// Turn off inlining when debugging - it obfuscates things +#ifdef DEBUG +# undef STATIC_INLINE +# define STATIC_INLINE static +#endif + +/* STATIC OBJECT LIST. + * + * During GC: + * We maintain a linked list of static objects that are still live. + * The requirements for this list are: + * + * - we need to scan the list while adding to it, in order to + * scavenge all the static objects (in the same way that + * breadth-first scavenging works for dynamic objects). + * + * - we need to be able to tell whether an object is already on + * the list, to break loops. + * + * Each static object has a "static link field", which we use for + * linking objects on to the list. We use a stack-type list, consing + * objects on the front as they are added (this means that the + * scavenge phase is depth-first, not breadth-first, but that + * shouldn't matter). + * + * A separate list is kept for objects that have been scavenged + * already - this is so that we can zero all the marks afterwards. + * + * An object is on the list if its static link field is non-zero; this + * means that we have to mark the end of the list with '1', not NULL. + * + * Extra notes for generational GC: + * + * Each generation has a static object list associated with it. When + * collecting generations up to N, we treat the static object lists + * from generations > N as roots. + * + * We build up a static object list while collecting generations 0..N, + * which is then appended to the static object list of generation N+1. + */ +static StgClosure* static_objects; // live static objects +StgClosure* scavenged_static_objects; // static objects scavenged so far + +/* N is the oldest generation being collected, where the generations + * are numbered starting at 0. A major GC (indicated by the major_gc + * flag) is when we're collecting all generations. We only attempt to + * deal with static objects and GC CAFs when doing a major GC. + */ +static nat N; +static rtsBool major_gc; + +/* Youngest generation that objects should be evacuated to in + * evacuate(). (Logically an argument to evacuate, but it's static + * a lot of the time so we optimise it into a global variable). + */ +static nat evac_gen; + +/* Whether to do eager promotion or not. + */ +static rtsBool eager_promotion; + +/* Weak pointers + */ +StgWeak *old_weak_ptr_list; // also pending finaliser list + +/* Which stage of processing various kinds of weak pointer are we at? + * (see traverse_weak_ptr_list() below for discussion). + */ +typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage; +static WeakStage weak_stage; + +/* List of all threads during GC + */ +static StgTSO *old_all_threads; +StgTSO *resurrected_threads; + +/* Flag indicating failure to evacuate an object to the desired + * generation. + */ +static rtsBool failed_to_evac; + +/* Saved nursery (used for 2-space collector only) + */ +static bdescr *saved_nursery; +static nat saved_n_blocks; + +/* Data used for allocation area sizing. + */ +static lnat new_blocks; // blocks allocated during this GC +static lnat new_scavd_blocks; // ditto, but depth-first blocks +static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC + +/* Used to avoid long recursion due to selector thunks + */ +static lnat thunk_selector_depth = 0; +#define MAX_THUNK_SELECTOR_DEPTH 8 + +/* Mut-list stats */ +#ifdef DEBUG +static nat + mutlist_MUTVARS, + mutlist_MUTARRS, + mutlist_OTHERS; +#endif + +/* ----------------------------------------------------------------------------- + Static function declarations + -------------------------------------------------------------------------- */ + +static bdescr * gc_alloc_block ( step *stp ); +static void mark_root ( StgClosure **root ); + +// Use a register argument for evacuate, if available. +#if __GNUC__ >= 2 +#define REGPARM1 __attribute__((regparm(1))) +#else +#define REGPARM1 +#endif + +REGPARM1 static StgClosure * evacuate (StgClosure *q); + +static void zero_static_object_list ( StgClosure* first_static ); + +static rtsBool traverse_weak_ptr_list ( void ); +static void mark_weak_ptr_list ( StgWeak **list ); + +static StgClosure * eval_thunk_selector ( nat field, StgSelector * p ); + + +static void scavenge ( step * ); +static void scavenge_mark_stack ( void ); +static void scavenge_stack ( StgPtr p, StgPtr stack_end ); +static rtsBool scavenge_one ( StgPtr p ); +static void scavenge_large ( step * ); +static void scavenge_static ( void ); +static void scavenge_mutable_list ( generation *g ); + +static void scavenge_large_bitmap ( StgPtr p, + StgLargeBitmap *large_bitmap, + nat size ); + +#if 0 && defined(DEBUG) +static void gcCAFs ( void ); +#endif + +/* ----------------------------------------------------------------------------- + inline functions etc. for dealing with the mark bitmap & stack. + -------------------------------------------------------------------------- */ + +#define MARK_STACK_BLOCKS 4 + +static bdescr *mark_stack_bdescr; +static StgPtr *mark_stack; +static StgPtr *mark_sp; +static StgPtr *mark_splim; + +// Flag and pointers used for falling back to a linear scan when the +// mark stack overflows. +static rtsBool mark_stack_overflowed; +static bdescr *oldgen_scan_bd; +static StgPtr oldgen_scan; + +STATIC_INLINE rtsBool +mark_stack_empty(void) +{ + return mark_sp == mark_stack; +} + +STATIC_INLINE rtsBool +mark_stack_full(void) +{ + return mark_sp >= mark_splim; +} + +STATIC_INLINE void +reset_mark_stack(void) +{ + mark_sp = mark_stack; +} + +STATIC_INLINE void +push_mark_stack(StgPtr p) +{ + *mark_sp++ = p; +} + +STATIC_INLINE StgPtr +pop_mark_stack(void) +{ + return *--mark_sp; +} + +/* ----------------------------------------------------------------------------- + Allocate a new to-space block in the given step. + -------------------------------------------------------------------------- */ + +static bdescr * +gc_alloc_block(step *stp) +{ + bdescr *bd = allocBlock(); + bd->gen_no = stp->gen_no; + bd->step = stp; + bd->link = NULL; + + // blocks in to-space in generations up to and including N + // get the BF_EVACUATED flag. + if (stp->gen_no <= N) { + bd->flags = BF_EVACUATED; + } else { + bd->flags = 0; + } + + // Start a new to-space block, chain it on after the previous one. + if (stp->hp_bd != NULL) { + stp->hp_bd->free = stp->hp; + stp->hp_bd->link = bd; + } + + stp->hp_bd = bd; + stp->hp = bd->start; + stp->hpLim = stp->hp + BLOCK_SIZE_W; + + stp->n_blocks++; + new_blocks++; + + return bd; +} + +static bdescr * +gc_alloc_scavd_block(step *stp) +{ + bdescr *bd = allocBlock(); + bd->gen_no = stp->gen_no; + bd->step = stp; + + // blocks in to-space in generations up to and including N + // get the BF_EVACUATED flag. + if (stp->gen_no <= N) { + bd->flags = BF_EVACUATED; + } else { + bd->flags = 0; + } + + bd->link = stp->blocks; + stp->blocks = bd; + + if (stp->scavd_hp != NULL) { + Bdescr(stp->scavd_hp)->free = stp->scavd_hp; + } + stp->scavd_hp = bd->start; + stp->scavd_hpLim = stp->scavd_hp + BLOCK_SIZE_W; + + stp->n_blocks++; + new_scavd_blocks++; + + return bd; +} + +/* ----------------------------------------------------------------------------- + GarbageCollect + + Rough outline of the algorithm: for garbage collecting generation N + (and all younger generations): + + - follow all pointers in the root set. the root set includes all + mutable objects in all generations (mutable_list). + + - for each pointer, evacuate the object it points to into either + + + to-space of the step given by step->to, which is the next + highest step in this generation or the first step in the next + generation if this is the last step. + + + to-space of generations[evac_gen]->steps[0], if evac_gen != 0. + When we evacuate an object we attempt to evacuate + everything it points to into the same generation - this is + achieved by setting evac_gen to the desired generation. If + we can't do this, then an entry in the mut list has to + be made for the cross-generation pointer. + + + if the object is already in a generation > N, then leave + it alone. + + - repeatedly scavenge to-space from each step in each generation + being collected until no more objects can be evacuated. + + - free from-space in each step, and set from-space = to-space. + + Locks held: all capabilities are held throughout GarbageCollect(). + + -------------------------------------------------------------------------- */ + +void +GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc ) +{ + bdescr *bd; + step *stp; + lnat live, allocated, copied = 0, scavd_copied = 0; + lnat oldgen_saved_blocks = 0; + nat g, s, i; + + ACQUIRE_SM_LOCK; + +#ifdef PROFILING + CostCentreStack *prev_CCS; +#endif + +#if defined(DEBUG) && defined(GRAN) + IF_DEBUG(gc, debugBelch("@@ Starting garbage collection at %ld (%lx)\n", + Now, Now)); +#endif + +#if defined(RTS_USER_SIGNALS) + // block signals + blockUserSignals(); +#endif + + // tell the STM to discard any cached closures its hoping to re-use + stmPreGCHook(); + + // tell the stats department that we've started a GC + stat_startGC(); + +#ifdef DEBUG + // check for memory leaks if DEBUG is on + memInventory(); +#endif + +#ifdef DEBUG + mutlist_MUTVARS = 0; + mutlist_MUTARRS = 0; + mutlist_OTHERS = 0; +#endif + + // Init stats and print par specific (timing) info + PAR_TICKY_PAR_START(); + + // attribute any costs to CCS_GC +#ifdef PROFILING + prev_CCS = CCCS; + CCCS = CCS_GC; +#endif + + /* Approximate how much we allocated. + * Todo: only when generating stats? + */ + allocated = calcAllocated(); + + /* Figure out which generation to collect + */ + if (force_major_gc) { + N = RtsFlags.GcFlags.generations - 1; + major_gc = rtsTrue; + } else { + N = 0; + for (g = 0; g < RtsFlags.GcFlags.generations; g++) { + if (generations[g].steps[0].n_blocks + + generations[g].steps[0].n_large_blocks + >= generations[g].max_blocks) { + N = g; + } + } + major_gc = (N == RtsFlags.GcFlags.generations-1); + } + +#ifdef RTS_GTK_FRONTPANEL + if (RtsFlags.GcFlags.frontpanel) { + updateFrontPanelBeforeGC(N); + } +#endif + + // check stack sanity *before* GC (ToDo: check all threads) +#if defined(GRAN) + // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity()); +#endif + IF_DEBUG(sanity, checkFreeListSanity()); + + /* Initialise the static object lists + */ + static_objects = END_OF_STATIC_LIST; + scavenged_static_objects = END_OF_STATIC_LIST; + + /* Save the nursery if we're doing a two-space collection. + * g0s0->blocks will be used for to-space, so we need to get the + * nursery out of the way. + */ + if (RtsFlags.GcFlags.generations == 1) { + saved_nursery = g0s0->blocks; + saved_n_blocks = g0s0->n_blocks; + g0s0->blocks = NULL; + g0s0->n_blocks = 0; + } + + /* Keep a count of how many new blocks we allocated during this GC + * (used for resizing the allocation area, later). + */ + new_blocks = 0; + new_scavd_blocks = 0; + + // Initialise to-space in all the generations/steps that we're + // collecting. + // + for (g = 0; g <= N; g++) { + + // throw away the mutable list. Invariant: the mutable list + // always has at least one block; this means we can avoid a check for + // NULL in recordMutable(). + if (g != 0) { + freeChain(generations[g].mut_list); + generations[g].mut_list = allocBlock(); + for (i = 0; i < n_capabilities; i++) { + freeChain(capabilities[i].mut_lists[g]); + capabilities[i].mut_lists[g] = allocBlock(); + } + } + + for (s = 0; s < generations[g].n_steps; s++) { + + // generation 0, step 0 doesn't need to-space + if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) { + continue; + } + + stp = &generations[g].steps[s]; + ASSERT(stp->gen_no == g); + + // start a new to-space for this step. + stp->old_blocks = stp->blocks; + stp->n_old_blocks = stp->n_blocks; + + // allocate the first to-space block; extra blocks will be + // chained on as necessary. + stp->hp_bd = NULL; + bd = gc_alloc_block(stp); + stp->blocks = bd; + stp->n_blocks = 1; + stp->scan = bd->start; + stp->scan_bd = bd; + + // allocate a block for "already scavenged" objects. This goes + // on the front of the stp->blocks list, so it won't be + // traversed by the scavenging sweep. + gc_alloc_scavd_block(stp); + + // initialise the large object queues. + stp->new_large_objects = NULL; + stp->scavenged_large_objects = NULL; + stp->n_scavenged_large_blocks = 0; + + // mark the large objects as not evacuated yet + for (bd = stp->large_objects; bd; bd = bd->link) { + bd->flags &= ~BF_EVACUATED; + } + + // for a compacted step, we need to allocate the bitmap + if (stp->is_compacted) { + nat bitmap_size; // in bytes + bdescr *bitmap_bdescr; + StgWord *bitmap; + + bitmap_size = stp->n_old_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE); + + if (bitmap_size > 0) { + bitmap_bdescr = allocGroup((lnat)BLOCK_ROUND_UP(bitmap_size) + / BLOCK_SIZE); + stp->bitmap = bitmap_bdescr; + bitmap = bitmap_bdescr->start; + + IF_DEBUG(gc, debugBelch("bitmap_size: %d, bitmap: %p", + bitmap_size, bitmap);); + + // don't forget to fill it with zeros! + memset(bitmap, 0, bitmap_size); + + // For each block in this step, point to its bitmap from the + // block descriptor. + for (bd=stp->old_blocks; bd != NULL; bd = bd->link) { + bd->u.bitmap = bitmap; + bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE); + + // Also at this point we set the BF_COMPACTED flag + // for this block. The invariant is that + // BF_COMPACTED is always unset, except during GC + // when it is set on those blocks which will be + // compacted. + bd->flags |= BF_COMPACTED; + } + } + } + } + } + + /* make sure the older generations have at least one block to + * allocate into (this makes things easier for copy(), see below). + */ + for (g = N+1; g < RtsFlags.GcFlags.generations; g++) { + for (s = 0; s < generations[g].n_steps; s++) { + stp = &generations[g].steps[s]; + if (stp->hp_bd == NULL) { + ASSERT(stp->blocks == NULL); + bd = gc_alloc_block(stp); + stp->blocks = bd; + stp->n_blocks = 1; + } + if (stp->scavd_hp == NULL) { + gc_alloc_scavd_block(stp); + stp->n_blocks++; + } + /* Set the scan pointer for older generations: remember we + * still have to scavenge objects that have been promoted. */ + stp->scan = stp->hp; + stp->scan_bd = stp->hp_bd; + stp->new_large_objects = NULL; + stp->scavenged_large_objects = NULL; + stp->n_scavenged_large_blocks = 0; + } + + /* Move the private mutable lists from each capability onto the + * main mutable list for the generation. + */ + for (i = 0; i < n_capabilities; i++) { + for (bd = capabilities[i].mut_lists[g]; + bd->link != NULL; bd = bd->link) { + /* nothing */ + } + bd->link = generations[g].mut_list; + generations[g].mut_list = capabilities[i].mut_lists[g]; + capabilities[i].mut_lists[g] = allocBlock(); + } + } + + /* Allocate a mark stack if we're doing a major collection. + */ + if (major_gc) { + mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS); + mark_stack = (StgPtr *)mark_stack_bdescr->start; + mark_sp = mark_stack; + mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W); + } else { + mark_stack_bdescr = NULL; + } + + eager_promotion = rtsTrue; // for now + + /* ----------------------------------------------------------------------- + * follow all the roots that we know about: + * - mutable lists from each generation > N + * we want to *scavenge* these roots, not evacuate them: they're not + * going to move in this GC. + * Also: do them in reverse generation order. This is because we + * often want to promote objects that are pointed to by older + * generations early, so we don't have to repeatedly copy them. + * Doing the generations in reverse order ensures that we don't end + * up in the situation where we want to evac an object to gen 3 and + * it has already been evaced to gen 2. + */ + { + int st; + for (g = RtsFlags.GcFlags.generations-1; g > N; g--) { + generations[g].saved_mut_list = generations[g].mut_list; + generations[g].mut_list = allocBlock(); + // mut_list always has at least one block. + } + + for (g = RtsFlags.GcFlags.generations-1; g > N; g--) { + IF_PAR_DEBUG(verbose, printMutableList(&generations[g])); + scavenge_mutable_list(&generations[g]); + evac_gen = g; + for (st = generations[g].n_steps-1; st >= 0; st--) { + scavenge(&generations[g].steps[st]); + } + } + } + + /* follow roots from the CAF list (used by GHCi) + */ + evac_gen = 0; + markCAFs(mark_root); + + /* follow all the roots that the application knows about. + */ + evac_gen = 0; + get_roots(mark_root); + +#if defined(PAR) + /* And don't forget to mark the TSO if we got here direct from + * Haskell! */ + /* Not needed in a seq version? + if (CurrentTSO) { + CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO); + } + */ + + // Mark the entries in the GALA table of the parallel system + markLocalGAs(major_gc); + // Mark all entries on the list of pending fetches + markPendingFetches(major_gc); +#endif + + /* Mark the weak pointer list, and prepare to detect dead weak + * pointers. + */ + mark_weak_ptr_list(&weak_ptr_list); + old_weak_ptr_list = weak_ptr_list; + weak_ptr_list = NULL; + weak_stage = WeakPtrs; + + /* The all_threads list is like the weak_ptr_list. + * See traverse_weak_ptr_list() for the details. + */ + old_all_threads = all_threads; + all_threads = END_TSO_QUEUE; + resurrected_threads = END_TSO_QUEUE; + + /* Mark the stable pointer table. + */ + markStablePtrTable(mark_root); + + /* ------------------------------------------------------------------------- + * Repeatedly scavenge all the areas we know about until there's no + * more scavenging to be done. + */ + { + rtsBool flag; + loop: + flag = rtsFalse; + + // scavenge static objects + if (major_gc && static_objects != END_OF_STATIC_LIST) { + IF_DEBUG(sanity, checkStaticObjects(static_objects)); + scavenge_static(); + } + + /* When scavenging the older generations: Objects may have been + * evacuated from generations <= N into older generations, and we + * need to scavenge these objects. We're going to try to ensure that + * any evacuations that occur move the objects into at least the + * same generation as the object being scavenged, otherwise we + * have to create new entries on the mutable list for the older + * generation. + */ + + // scavenge each step in generations 0..maxgen + { + long gen; + int st; + + loop2: + // scavenge objects in compacted generation + if (mark_stack_overflowed || oldgen_scan_bd != NULL || + (mark_stack_bdescr != NULL && !mark_stack_empty())) { + scavenge_mark_stack(); + flag = rtsTrue; + } + + for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) { + for (st = generations[gen].n_steps; --st >= 0; ) { + if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) { + continue; + } + stp = &generations[gen].steps[st]; + evac_gen = gen; + if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) { + scavenge(stp); + flag = rtsTrue; + goto loop2; + } + if (stp->new_large_objects != NULL) { + scavenge_large(stp); + flag = rtsTrue; + goto loop2; + } + } + } + } + + if (flag) { goto loop; } + + // must be last... invariant is that everything is fully + // scavenged at this point. + if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something + goto loop; + } + } + + /* Update the pointers from the task list - these are + * treated as weak pointers because we want to allow a main thread + * to get a BlockedOnDeadMVar exception in the same way as any other + * thread. Note that the threads should all have been retained by + * GC by virtue of being on the all_threads list, we're just + * updating pointers here. + */ + { + Task *task; + StgTSO *tso; + for (task = all_tasks; task != NULL; task = task->all_link) { + if (!task->stopped && task->tso) { + ASSERT(task->tso->bound == task); + tso = (StgTSO *) isAlive((StgClosure *)task->tso); + if (tso == NULL) { + barf("task %p: main thread %d has been GC'd", +#ifdef THREADED_RTS + (void *)task->id, +#else + (void *)task, +#endif + task->tso->id); + } + task->tso = tso; + } + } + } + +#if defined(PAR) + // Reconstruct the Global Address tables used in GUM + rebuildGAtables(major_gc); + IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/)); +#endif + + // Now see which stable names are still alive. + gcStablePtrTable(); + + // Tidy the end of the to-space chains + for (g = 0; g < RtsFlags.GcFlags.generations; g++) { + for (s = 0; s < generations[g].n_steps; s++) { + stp = &generations[g].steps[s]; + if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) { + ASSERT(Bdescr(stp->hp) == stp->hp_bd); + stp->hp_bd->free = stp->hp; + Bdescr(stp->scavd_hp)->free = stp->scavd_hp; + } + } + } + +#ifdef PROFILING + // We call processHeapClosureForDead() on every closure destroyed during + // the current garbage collection, so we invoke LdvCensusForDead(). + if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV + || RtsFlags.ProfFlags.bioSelector != NULL) + LdvCensusForDead(N); +#endif + + // NO MORE EVACUATION AFTER THIS POINT! + // Finally: compaction of the oldest generation. + if (major_gc && oldest_gen->steps[0].is_compacted) { + // save number of blocks for stats + oldgen_saved_blocks = oldest_gen->steps[0].n_old_blocks; + compact(get_roots); + } + + IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse)); + + /* run through all the generations/steps and tidy up + */ + copied = new_blocks * BLOCK_SIZE_W; + scavd_copied = new_scavd_blocks * BLOCK_SIZE_W; + for (g = 0; g < RtsFlags.GcFlags.generations; g++) { + + if (g <= N) { + generations[g].collections++; // for stats + } + + // Count the mutable list as bytes "copied" for the purposes of + // stats. Every mutable list is copied during every GC. + if (g > 0) { + nat mut_list_size = 0; + for (bd = generations[g].mut_list; bd != NULL; bd = bd->link) { + mut_list_size += bd->free - bd->start; + } + copied += mut_list_size; + + IF_DEBUG(gc, debugBelch("mut_list_size: %ld (%d vars, %d arrays, %d others)\n", mut_list_size * sizeof(W_), mutlist_MUTVARS, mutlist_MUTARRS, mutlist_OTHERS)); + } + + for (s = 0; s < generations[g].n_steps; s++) { + bdescr *next; + stp = &generations[g].steps[s]; + + if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) { + // stats information: how much we copied + if (g <= N) { + copied -= stp->hp_bd->start + BLOCK_SIZE_W - + stp->hp_bd->free; + scavd_copied -= (P_)(BLOCK_ROUND_UP(stp->scavd_hp)) - stp->scavd_hp; + } + } + + // for generations we collected... + if (g <= N) { + + /* free old memory and shift to-space into from-space for all + * the collected steps (except the allocation area). These + * freed blocks will probaby be quickly recycled. + */ + if (!(g == 0 && s == 0)) { + if (stp->is_compacted) { + // for a compacted step, just shift the new to-space + // onto the front of the now-compacted existing blocks. + for (bd = stp->blocks; bd != NULL; bd = bd->link) { + bd->flags &= ~BF_EVACUATED; // now from-space + } + // tack the new blocks on the end of the existing blocks + if (stp->old_blocks != NULL) { + for (bd = stp->old_blocks; bd != NULL; bd = next) { + // NB. this step might not be compacted next + // time, so reset the BF_COMPACTED flags. + // They are set before GC if we're going to + // compact. (search for BF_COMPACTED above). + bd->flags &= ~BF_COMPACTED; + next = bd->link; + if (next == NULL) { + bd->link = stp->blocks; + } + } + stp->blocks = stp->old_blocks; + } + // add the new blocks to the block tally + stp->n_blocks += stp->n_old_blocks; + ASSERT(countBlocks(stp->blocks) == stp->n_blocks); + } else { + freeChain(stp->old_blocks); + for (bd = stp->blocks; bd != NULL; bd = bd->link) { + bd->flags &= ~BF_EVACUATED; // now from-space + } + } + stp->old_blocks = NULL; + stp->n_old_blocks = 0; + } + + /* LARGE OBJECTS. The current live large objects are chained on + * scavenged_large, having been moved during garbage + * collection from large_objects. Any objects left on + * large_objects list are therefore dead, so we free them here. + */ + for (bd = stp->large_objects; bd != NULL; bd = next) { + next = bd->link; + freeGroup(bd); + bd = next; + } + + // update the count of blocks used by large objects + for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) { + bd->flags &= ~BF_EVACUATED; + } + stp->large_objects = stp->scavenged_large_objects; + stp->n_large_blocks = stp->n_scavenged_large_blocks; + + } else { + // for older generations... + + /* For older generations, we need to append the + * scavenged_large_object list (i.e. large objects that have been + * promoted during this GC) to the large_object list for that step. + */ + for (bd = stp->scavenged_large_objects; bd; bd = next) { + next = bd->link; + bd->flags &= ~BF_EVACUATED; + dbl_link_onto(bd, &stp->large_objects); + } + + // add the new blocks we promoted during this GC + stp->n_large_blocks += stp->n_scavenged_large_blocks; + } + } + } + + /* Reset the sizes of the older generations when we do a major + * collection. + * + * CURRENT STRATEGY: make all generations except zero the same size. + * We have to stay within the maximum heap size, and leave a certain + * percentage of the maximum heap size available to allocate into. + */ + if (major_gc && RtsFlags.GcFlags.generations > 1) { + nat live, size, min_alloc; + nat max = RtsFlags.GcFlags.maxHeapSize; + nat gens = RtsFlags.GcFlags.generations; + + // live in the oldest generations + live = oldest_gen->steps[0].n_blocks + + oldest_gen->steps[0].n_large_blocks; + + // default max size for all generations except zero + size = stg_max(live * RtsFlags.GcFlags.oldGenFactor, + RtsFlags.GcFlags.minOldGenSize); + + // minimum size for generation zero + min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200, + RtsFlags.GcFlags.minAllocAreaSize); + + // Auto-enable compaction when the residency reaches a + // certain percentage of the maximum heap size (default: 30%). + if (RtsFlags.GcFlags.generations > 1 && + (RtsFlags.GcFlags.compact || + (max > 0 && + oldest_gen->steps[0].n_blocks > + (RtsFlags.GcFlags.compactThreshold * max) / 100))) { + oldest_gen->steps[0].is_compacted = 1; +// debugBelch("compaction: on\n", live); + } else { + oldest_gen->steps[0].is_compacted = 0; +// debugBelch("compaction: off\n", live); + } + + // if we're going to go over the maximum heap size, reduce the + // size of the generations accordingly. The calculation is + // different if compaction is turned on, because we don't need + // to double the space required to collect the old generation. + if (max != 0) { + + // this test is necessary to ensure that the calculations + // below don't have any negative results - we're working + // with unsigned values here. + if (max < min_alloc) { + heapOverflow(); + } + + if (oldest_gen->steps[0].is_compacted) { + if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) { + size = (max - min_alloc) / ((gens - 1) * 2 - 1); + } + } else { + if ( (size * (gens - 1) * 2) + min_alloc > max ) { + size = (max - min_alloc) / ((gens - 1) * 2); + } + } + + if (size < live) { + heapOverflow(); + } + } + +#if 0 + debugBelch("live: %d, min_alloc: %d, size : %d, max = %d\n", live, + min_alloc, size, max); +#endif + + for (g = 0; g < gens; g++) { + generations[g].max_blocks = size; + } + } + + // Guess the amount of live data for stats. + live = calcLive(); + + /* Free the small objects allocated via allocate(), since this will + * all have been copied into G0S1 now. + */ + if (small_alloc_list != NULL) { + freeChain(small_alloc_list); + } + small_alloc_list = NULL; + alloc_blocks = 0; + alloc_Hp = NULL; + alloc_HpLim = NULL; + alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize; + + // Start a new pinned_object_block + pinned_object_block = NULL; + + /* Free the mark stack. + */ + if (mark_stack_bdescr != NULL) { + freeGroup(mark_stack_bdescr); + } + + /* Free any bitmaps. + */ + for (g = 0; g <= N; g++) { + for (s = 0; s < generations[g].n_steps; s++) { + stp = &generations[g].steps[s]; + if (stp->bitmap != NULL) { + freeGroup(stp->bitmap); + stp->bitmap = NULL; + } + } + } + + /* Two-space collector: + * Free the old to-space, and estimate the amount of live data. + */ + if (RtsFlags.GcFlags.generations == 1) { + nat blocks; + + if (g0s0->old_blocks != NULL) { + freeChain(g0s0->old_blocks); + } + for (bd = g0s0->blocks; bd != NULL; bd = bd->link) { + bd->flags = 0; // now from-space + } + g0s0->old_blocks = g0s0->blocks; + g0s0->n_old_blocks = g0s0->n_blocks; + g0s0->blocks = saved_nursery; + g0s0->n_blocks = saved_n_blocks; + + /* For a two-space collector, we need to resize the nursery. */ + + /* set up a new nursery. Allocate a nursery size based on a + * function of the amount of live data (by default a factor of 2) + * Use the blocks from the old nursery if possible, freeing up any + * left over blocks. + * + * If we get near the maximum heap size, then adjust our nursery + * size accordingly. If the nursery is the same size as the live + * data (L), then we need 3L bytes. We can reduce the size of the + * nursery to bring the required memory down near 2L bytes. + * + * A normal 2-space collector would need 4L bytes to give the same + * performance we get from 3L bytes, reducing to the same + * performance at 2L bytes. + */ + blocks = g0s0->n_old_blocks; + + if ( RtsFlags.GcFlags.maxHeapSize != 0 && + blocks * RtsFlags.GcFlags.oldGenFactor * 2 > + RtsFlags.GcFlags.maxHeapSize ) { + long adjusted_blocks; // signed on purpose + int pc_free; + + adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks); + IF_DEBUG(gc, debugBelch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks)); + pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize; + if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ { + heapOverflow(); + } + blocks = adjusted_blocks; + + } else { + blocks *= RtsFlags.GcFlags.oldGenFactor; + if (blocks < RtsFlags.GcFlags.minAllocAreaSize) { + blocks = RtsFlags.GcFlags.minAllocAreaSize; + } + } + resizeNurseries(blocks); + + } else { + /* Generational collector: + * If the user has given us a suggested heap size, adjust our + * allocation area to make best use of the memory available. + */ + + if (RtsFlags.GcFlags.heapSizeSuggestion) { + long blocks; + nat needed = calcNeeded(); // approx blocks needed at next GC + + /* Guess how much will be live in generation 0 step 0 next time. + * A good approximation is obtained by finding the + * percentage of g0s0 that was live at the last minor GC. + */ + if (N == 0) { + g0s0_pcnt_kept = (new_blocks * 100) / countNurseryBlocks(); + } + + /* Estimate a size for the allocation area based on the + * information available. We might end up going slightly under + * or over the suggested heap size, but we should be pretty + * close on average. + * + * Formula: suggested - needed + * ---------------------------- + * 1 + g0s0_pcnt_kept/100 + * + * where 'needed' is the amount of memory needed at the next + * collection for collecting all steps except g0s0. + */ + blocks = + (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) / + (100 + (long)g0s0_pcnt_kept); + + if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) { + blocks = RtsFlags.GcFlags.minAllocAreaSize; + } + + resizeNurseries((nat)blocks); + + } else { + // we might have added extra large blocks to the nursery, so + // resize back to minAllocAreaSize again. + resizeNurseriesFixed(RtsFlags.GcFlags.minAllocAreaSize); + } + } + + // mark the garbage collected CAFs as dead +#if 0 && defined(DEBUG) // doesn't work at the moment + if (major_gc) { gcCAFs(); } +#endif + +#ifdef PROFILING + // resetStaticObjectForRetainerProfiling() must be called before + // zeroing below. + resetStaticObjectForRetainerProfiling(); +#endif + + // zero the scavenged static object list + if (major_gc) { + zero_static_object_list(scavenged_static_objects); + } + + // Reset the nursery + resetNurseries(); + + // start any pending finalizers + RELEASE_SM_LOCK; + scheduleFinalizers(last_free_capability, old_weak_ptr_list); + ACQUIRE_SM_LOCK; + + // send exceptions to any threads which were about to die + RELEASE_SM_LOCK; + resurrectThreads(resurrected_threads); + ACQUIRE_SM_LOCK; + + // Update the stable pointer hash table. + updateStablePtrTable(major_gc); + + // check sanity after GC + IF_DEBUG(sanity, checkSanity()); + + // extra GC trace info + IF_DEBUG(gc, statDescribeGens()); + +#ifdef DEBUG + // symbol-table based profiling + /* heapCensus(to_blocks); */ /* ToDo */ +#endif + + // restore enclosing cost centre +#ifdef PROFILING + CCCS = prev_CCS; +#endif + +#ifdef DEBUG + // check for memory leaks if DEBUG is on + memInventory(); +#endif + +#ifdef RTS_GTK_FRONTPANEL + if (RtsFlags.GcFlags.frontpanel) { + updateFrontPanelAfterGC( N, live ); + } +#endif + + // ok, GC over: tell the stats department what happened. + stat_endGC(allocated, live, copied, scavd_copied, N); + +#if defined(RTS_USER_SIGNALS) + // unblock signals again + unblockUserSignals(); +#endif + + RELEASE_SM_LOCK; + + //PAR_TICKY_TP(); +} + + +/* ----------------------------------------------------------------------------- + Weak Pointers + + traverse_weak_ptr_list is called possibly many times during garbage + collection. It returns a flag indicating whether it did any work + (i.e. called evacuate on any live pointers). + + Invariant: traverse_weak_ptr_list is called when the heap is in an + idempotent state. That means that there are no pending + evacuate/scavenge operations. This invariant helps the weak + pointer code decide which weak pointers are dead - if there are no + new live weak pointers, then all the currently unreachable ones are + dead. + + For generational GC: we just don't try to finalize weak pointers in + older generations than the one we're collecting. This could + probably be optimised by keeping per-generation lists of weak + pointers, but for a few weak pointers this scheme will work. + + There are three distinct stages to processing weak pointers: + + - weak_stage == WeakPtrs + + We process all the weak pointers whos keys are alive (evacuate + their values and finalizers), and repeat until we can find no new + live keys. If no live keys are found in this pass, then we + evacuate the finalizers of all the dead weak pointers in order to + run them. + + - weak_stage == WeakThreads + + Now, we discover which *threads* are still alive. Pointers to + threads from the all_threads and main thread lists are the + weakest of all: a pointers from the finalizer of a dead weak + pointer can keep a thread alive. Any threads found to be unreachable + are evacuated and placed on the resurrected_threads list so we + can send them a signal later. + + - weak_stage == WeakDone + + No more evacuation is done. + + -------------------------------------------------------------------------- */ + +static rtsBool +traverse_weak_ptr_list(void) +{ + StgWeak *w, **last_w, *next_w; + StgClosure *new; + rtsBool flag = rtsFalse; + + switch (weak_stage) { + + case WeakDone: + return rtsFalse; + + case WeakPtrs: + /* doesn't matter where we evacuate values/finalizers to, since + * these pointers are treated as roots (iff the keys are alive). + */ + evac_gen = 0; + + last_w = &old_weak_ptr_list; + for (w = old_weak_ptr_list; w != NULL; w = next_w) { + + /* There might be a DEAD_WEAK on the list if finalizeWeak# was + * called on a live weak pointer object. Just remove it. + */ + if (w->header.info == &stg_DEAD_WEAK_info) { + next_w = ((StgDeadWeak *)w)->link; + *last_w = next_w; + continue; + } + + switch (get_itbl(w)->type) { + + case EVACUATED: + next_w = (StgWeak *)((StgEvacuated *)w)->evacuee; + *last_w = next_w; + continue; + + case WEAK: + /* Now, check whether the key is reachable. + */ + new = isAlive(w->key); + if (new != NULL) { + w->key = new; + // evacuate the value and finalizer + w->value = evacuate(w->value); + w->finalizer = evacuate(w->finalizer); + // remove this weak ptr from the old_weak_ptr list + *last_w = w->link; + // and put it on the new weak ptr list + next_w = w->link; + w->link = weak_ptr_list; + weak_ptr_list = w; + flag = rtsTrue; + IF_DEBUG(weak, debugBelch("Weak pointer still alive at %p -> %p", + w, w->key)); + continue; + } + else { + last_w = &(w->link); + next_w = w->link; + continue; + } + + default: + barf("traverse_weak_ptr_list: not WEAK"); + } + } + + /* If we didn't make any changes, then we can go round and kill all + * the dead weak pointers. The old_weak_ptr list is used as a list + * of pending finalizers later on. + */ + if (flag == rtsFalse) { + for (w = old_weak_ptr_list; w; w = w->link) { + w->finalizer = evacuate(w->finalizer); + } + + // Next, move to the WeakThreads stage after fully + // scavenging the finalizers we've just evacuated. + weak_stage = WeakThreads; + } + + return rtsTrue; + + case WeakThreads: + /* Now deal with the all_threads list, which behaves somewhat like + * the weak ptr list. If we discover any threads that are about to + * become garbage, we wake them up and administer an exception. + */ + { + StgTSO *t, *tmp, *next, **prev; + + prev = &old_all_threads; + for (t = old_all_threads; t != END_TSO_QUEUE; t = next) { + + tmp = (StgTSO *)isAlive((StgClosure *)t); + + if (tmp != NULL) { + t = tmp; + } + + ASSERT(get_itbl(t)->type == TSO); + switch (t->what_next) { + case ThreadRelocated: + next = t->link; + *prev = next; + continue; + case ThreadKilled: + case ThreadComplete: + // finshed or died. The thread might still be alive, but we + // don't keep it on the all_threads list. Don't forget to + // stub out its global_link field. + next = t->global_link; + t->global_link = END_TSO_QUEUE; + *prev = next; + continue; + default: + ; + } + + // Threads blocked on black holes: if the black hole + // is alive, then the thread is alive too. + if (tmp == NULL && t->why_blocked == BlockedOnBlackHole) { + if (isAlive(t->block_info.closure)) { + t = (StgTSO *)evacuate((StgClosure *)t); + tmp = t; + flag = rtsTrue; + } + } + + if (tmp == NULL) { + // not alive (yet): leave this thread on the + // old_all_threads list. + prev = &(t->global_link); + next = t->global_link; + } + else { + // alive: move this thread onto the all_threads list. + next = t->global_link; + t->global_link = all_threads; + all_threads = t; + *prev = next; + } + } + } + + /* If we evacuated any threads, we need to go back to the scavenger. + */ + if (flag) return rtsTrue; + + /* And resurrect any threads which were about to become garbage. + */ + { + StgTSO *t, *tmp, *next; + for (t = old_all_threads; t != END_TSO_QUEUE; t = next) { + next = t->global_link; + tmp = (StgTSO *)evacuate((StgClosure *)t); + tmp->global_link = resurrected_threads; + resurrected_threads = tmp; + } + } + + /* Finally, we can update the blackhole_queue. This queue + * simply strings together TSOs blocked on black holes, it is + * not intended to keep anything alive. Hence, we do not follow + * pointers on the blackhole_queue until now, when we have + * determined which TSOs are otherwise reachable. We know at + * this point that all TSOs have been evacuated, however. + */ + { + StgTSO **pt; + for (pt = &blackhole_queue; *pt != END_TSO_QUEUE; pt = &((*pt)->link)) { + *pt = (StgTSO *)isAlive((StgClosure *)*pt); + ASSERT(*pt != NULL); + } + } + + weak_stage = WeakDone; // *now* we're done, + return rtsTrue; // but one more round of scavenging, please + + default: + barf("traverse_weak_ptr_list"); + return rtsTrue; + } + +} + +/* ----------------------------------------------------------------------------- + After GC, the live weak pointer list may have forwarding pointers + on it, because a weak pointer object was evacuated after being + moved to the live weak pointer list. We remove those forwarding + pointers here. + + Also, we don't consider weak pointer objects to be reachable, but + we must nevertheless consider them to be "live" and retain them. + Therefore any weak pointer objects which haven't as yet been + evacuated need to be evacuated now. + -------------------------------------------------------------------------- */ + + +static void +mark_weak_ptr_list ( StgWeak **list ) +{ + StgWeak *w, **last_w; + + last_w = list; + for (w = *list; w; w = w->link) { + // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here + ASSERT(w->header.info == &stg_DEAD_WEAK_info + || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED); + w = (StgWeak *)evacuate((StgClosure *)w); + *last_w = w; + last_w = &(w->link); + } +} + +/* ----------------------------------------------------------------------------- + isAlive determines whether the given closure is still alive (after + a garbage collection) or not. It returns the new address of the + closure if it is alive, or NULL otherwise. + + NOTE: Use it before compaction only! + -------------------------------------------------------------------------- */ + + +StgClosure * +isAlive(StgClosure *p) +{ + const StgInfoTable *info; + bdescr *bd; + + while (1) { + + ASSERT(LOOKS_LIKE_CLOSURE_PTR(p)); + info = get_itbl(p); + + // ignore static closures + // + // ToDo: for static closures, check the static link field. + // Problem here is that we sometimes don't set the link field, eg. + // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs. + // + if (!HEAP_ALLOCED(p)) { + return p; + } + + // ignore closures in generations that we're not collecting. + bd = Bdescr((P_)p); + if (bd->gen_no > N) { + return p; + } + + // if it's a pointer into to-space, then we're done + if (bd->flags & BF_EVACUATED) { + return p; + } + + // large objects use the evacuated flag + if (bd->flags & BF_LARGE) { + return NULL; + } + + // check the mark bit for compacted steps + if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) { + return p; + } + + switch (info->type) { + + case IND: + case IND_STATIC: + case IND_PERM: + case IND_OLDGEN: // rely on compatible layout with StgInd + case IND_OLDGEN_PERM: + // follow indirections + p = ((StgInd *)p)->indirectee; + continue; + + case EVACUATED: + // alive! + return ((StgEvacuated *)p)->evacuee; + + case TSO: + if (((StgTSO *)p)->what_next == ThreadRelocated) { + p = (StgClosure *)((StgTSO *)p)->link; + continue; + } + return NULL; + + default: + // dead. + return NULL; + } + } +} + +static void +mark_root(StgClosure **root) +{ + *root = evacuate(*root); +} + +STATIC_INLINE void +upd_evacuee(StgClosure *p, StgClosure *dest) +{ + // not true: (ToDo: perhaps it should be) + // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED); + SET_INFO(p, &stg_EVACUATED_info); + ((StgEvacuated *)p)->evacuee = dest; +} + + +STATIC_INLINE StgClosure * +copy(StgClosure *src, nat size, step *stp) +{ + StgPtr to, from; + nat i; +#ifdef PROFILING + // @LDV profiling + nat size_org = size; +#endif + + TICK_GC_WORDS_COPIED(size); + /* Find out where we're going, using the handy "to" pointer in + * the step of the source object. If it turns out we need to + * evacuate to an older generation, adjust it here (see comment + * by evacuate()). + */ + if (stp->gen_no < evac_gen) { + if (eager_promotion) { + stp = &generations[evac_gen].steps[0]; + } else { + failed_to_evac = rtsTrue; + } + } + + /* chain a new block onto the to-space for the destination step if + * necessary. + */ + if (stp->hp + size >= stp->hpLim) { + gc_alloc_block(stp); + } + + to = stp->hp; + from = (StgPtr)src; + stp->hp = to + size; + for (i = 0; i < size; i++) { // unroll for small i + to[i] = from[i]; + } + upd_evacuee((StgClosure *)from,(StgClosure *)to); + +#ifdef PROFILING + // We store the size of the just evacuated object in the LDV word so that + // the profiler can guess the position of the next object later. + SET_EVACUAEE_FOR_LDV(from, size_org); +#endif + return (StgClosure *)to; +} + +// Same as copy() above, except the object will be allocated in memory +// that will not be scavenged. Used for object that have no pointer +// fields. +STATIC_INLINE StgClosure * +copy_noscav(StgClosure *src, nat size, step *stp) +{ + StgPtr to, from; + nat i; +#ifdef PROFILING + // @LDV profiling + nat size_org = size; +#endif + + TICK_GC_WORDS_COPIED(size); + /* Find out where we're going, using the handy "to" pointer in + * the step of the source object. If it turns out we need to + * evacuate to an older generation, adjust it here (see comment + * by evacuate()). + */ + if (stp->gen_no < evac_gen) { + if (eager_promotion) { + stp = &generations[evac_gen].steps[0]; + } else { + failed_to_evac = rtsTrue; + } + } + + /* chain a new block onto the to-space for the destination step if + * necessary. + */ + if (stp->scavd_hp + size >= stp->scavd_hpLim) { + gc_alloc_scavd_block(stp); + } + + to = stp->scavd_hp; + from = (StgPtr)src; + stp->scavd_hp = to + size; + for (i = 0; i < size; i++) { // unroll for small i + to[i] = from[i]; + } + upd_evacuee((StgClosure *)from,(StgClosure *)to); + +#ifdef PROFILING + // We store the size of the just evacuated object in the LDV word so that + // the profiler can guess the position of the next object later. + SET_EVACUAEE_FOR_LDV(from, size_org); +#endif + return (StgClosure *)to; +} + +/* Special version of copy() for when we only want to copy the info + * pointer of an object, but reserve some padding after it. This is + * used to optimise evacuation of BLACKHOLEs. + */ + + +static StgClosure * +copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp) +{ + P_ dest, to, from; +#ifdef PROFILING + // @LDV profiling + nat size_to_copy_org = size_to_copy; +#endif + + TICK_GC_WORDS_COPIED(size_to_copy); + if (stp->gen_no < evac_gen) { + if (eager_promotion) { + stp = &generations[evac_gen].steps[0]; + } else { + failed_to_evac = rtsTrue; + } + } + + if (stp->hp + size_to_reserve >= stp->hpLim) { + gc_alloc_block(stp); + } + + for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) { + *to++ = *from++; + } + + dest = stp->hp; + stp->hp += size_to_reserve; + upd_evacuee(src,(StgClosure *)dest); +#ifdef PROFILING + // We store the size of the just evacuated object in the LDV word so that + // the profiler can guess the position of the next object later. + // size_to_copy_org is wrong because the closure already occupies size_to_reserve + // words. + SET_EVACUAEE_FOR_LDV(src, size_to_reserve); + // fill the slop + if (size_to_reserve - size_to_copy_org > 0) + LDV_FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org)); +#endif + return (StgClosure *)dest; +} + + +/* ----------------------------------------------------------------------------- + Evacuate a large object + + This just consists of removing the object from the (doubly-linked) + step->large_objects list, and linking it on to the (singly-linked) + step->new_large_objects list, from where it will be scavenged later. + + Convention: bd->flags has BF_EVACUATED set for a large object + that has been evacuated, or unset otherwise. + -------------------------------------------------------------------------- */ + + +STATIC_INLINE void +evacuate_large(StgPtr p) +{ + bdescr *bd = Bdescr(p); + step *stp; + + // object must be at the beginning of the block (or be a ByteArray) + ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS || + (((W_)p & BLOCK_MASK) == 0)); + + // already evacuated? + if (bd->flags & BF_EVACUATED) { + /* Don't forget to set the failed_to_evac flag if we didn't get + * the desired destination (see comments in evacuate()). + */ + if (bd->gen_no < evac_gen) { + failed_to_evac = rtsTrue; + TICK_GC_FAILED_PROMOTION(); + } + return; + } + + stp = bd->step; + // remove from large_object list + if (bd->u.back) { + bd->u.back->link = bd->link; + } else { // first object in the list + stp->large_objects = bd->link; + } + if (bd->link) { + bd->link->u.back = bd->u.back; + } + + /* link it on to the evacuated large object list of the destination step + */ + stp = bd->step->to; + if (stp->gen_no < evac_gen) { + if (eager_promotion) { + stp = &generations[evac_gen].steps[0]; + } else { + failed_to_evac = rtsTrue; + } + } + + bd->step = stp; + bd->gen_no = stp->gen_no; + bd->link = stp->new_large_objects; + stp->new_large_objects = bd; + bd->flags |= BF_EVACUATED; +} + +/* ----------------------------------------------------------------------------- + Evacuate + + This is called (eventually) for every live object in the system. + + The caller to evacuate specifies a desired generation in the + evac_gen global variable. The following conditions apply to + evacuating an object which resides in generation M when we're + collecting up to generation N + + if M >= evac_gen + if M > N do nothing + else evac to step->to + + if M < evac_gen evac to evac_gen, step 0 + + if the object is already evacuated, then we check which generation + it now resides in. + + if M >= evac_gen do nothing + if M < evac_gen set failed_to_evac flag to indicate that we + didn't manage to evacuate this object into evac_gen. + + + OPTIMISATION NOTES: + + evacuate() is the single most important function performance-wise + in the GC. Various things have been tried to speed it up, but as + far as I can tell the code generated by gcc 3.2 with -O2 is about + as good as it's going to get. We pass the argument to evacuate() + in a register using the 'regparm' attribute (see the prototype for + evacuate() near the top of this file). + + Changing evacuate() to take an (StgClosure **) rather than + returning the new pointer seems attractive, because we can avoid + writing back the pointer when it hasn't changed (eg. for a static + object, or an object in a generation > N). However, I tried it and + it doesn't help. One reason is that the (StgClosure **) pointer + gets spilled to the stack inside evacuate(), resulting in far more + extra reads/writes than we save. + -------------------------------------------------------------------------- */ + +REGPARM1 static StgClosure * +evacuate(StgClosure *q) +{ +#if defined(PAR) + StgClosure *to; +#endif + bdescr *bd = NULL; + step *stp; + const StgInfoTable *info; + +loop: + ASSERT(LOOKS_LIKE_CLOSURE_PTR(q)); + + if (!HEAP_ALLOCED(q)) { + + if (!major_gc) return q; + + info = get_itbl(q); + switch (info->type) { + + case THUNK_STATIC: + if (info->srt_bitmap != 0 && + *THUNK_STATIC_LINK((StgClosure *)q) == NULL) { + *THUNK_STATIC_LINK((StgClosure *)q) = static_objects; + static_objects = (StgClosure *)q; + } + return q; + + case FUN_STATIC: + if (info->srt_bitmap != 0 && + *FUN_STATIC_LINK((StgClosure *)q) == NULL) { + *FUN_STATIC_LINK((StgClosure *)q) = static_objects; + static_objects = (StgClosure *)q; + } + return q; + + case IND_STATIC: + /* If q->saved_info != NULL, then it's a revertible CAF - it'll be + * on the CAF list, so don't do anything with it here (we'll + * scavenge it later). + */ + if (((StgIndStatic *)q)->saved_info == NULL + && *IND_STATIC_LINK((StgClosure *)q) == NULL) { + *IND_STATIC_LINK((StgClosure *)q) = static_objects; + static_objects = (StgClosure *)q; + } + return q; + + case CONSTR_STATIC: + if (*STATIC_LINK(info,(StgClosure *)q) == NULL) { + *STATIC_LINK(info,(StgClosure *)q) = static_objects; + static_objects = (StgClosure *)q; + } + return q; + + case CONSTR_INTLIKE: + case CONSTR_CHARLIKE: + case CONSTR_NOCAF_STATIC: + /* no need to put these on the static linked list, they don't need + * to be scavenged. + */ + return q; + + default: + barf("evacuate(static): strange closure type %d", (int)(info->type)); + } + } + + bd = Bdescr((P_)q); + + if (bd->gen_no > N) { + /* Can't evacuate this object, because it's in a generation + * older than the ones we're collecting. Let's hope that it's + * in evac_gen or older, or we will have to arrange to track + * this pointer using the mutable list. + */ + if (bd->gen_no < evac_gen) { + // nope + failed_to_evac = rtsTrue; + TICK_GC_FAILED_PROMOTION(); + } + return q; + } + + if ((bd->flags & (BF_LARGE | BF_COMPACTED | BF_EVACUATED)) != 0) { + + /* pointer into to-space: just return it. This normally + * shouldn't happen, but alllowing it makes certain things + * slightly easier (eg. the mutable list can contain the same + * object twice, for example). + */ + if (bd->flags & BF_EVACUATED) { + if (bd->gen_no < evac_gen) { + failed_to_evac = rtsTrue; + TICK_GC_FAILED_PROMOTION(); + } + return q; + } + + /* evacuate large objects by re-linking them onto a different list. + */ + if (bd->flags & BF_LARGE) { + info = get_itbl(q); + if (info->type == TSO && + ((StgTSO *)q)->what_next == ThreadRelocated) { + q = (StgClosure *)((StgTSO *)q)->link; + goto loop; + } + evacuate_large((P_)q); + return q; + } + + /* If the object is in a step that we're compacting, then we + * need to use an alternative evacuate procedure. + */ + if (bd->flags & BF_COMPACTED) { + if (!is_marked((P_)q,bd)) { + mark((P_)q,bd); + if (mark_stack_full()) { + mark_stack_overflowed = rtsTrue; + reset_mark_stack(); + } + push_mark_stack((P_)q); + } + return q; + } + } + + stp = bd->step->to; + + info = get_itbl(q); + + switch (info->type) { + + case MUT_VAR_CLEAN: + case MUT_VAR_DIRTY: + case MVAR: + return copy(q,sizeW_fromITBL(info),stp); + + case CONSTR_0_1: + { + StgWord w = (StgWord)q->payload[0]; + if (q->header.info == Czh_con_info && + // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE && + (StgChar)w <= MAX_CHARLIKE) { + return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w); + } + if (q->header.info == Izh_con_info && + (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) { + return (StgClosure *)INTLIKE_CLOSURE((StgInt)w); + } + // else + return copy_noscav(q,sizeofW(StgHeader)+1,stp); + } + + case FUN_0_1: + case FUN_1_0: + case CONSTR_1_0: + return copy(q,sizeofW(StgHeader)+1,stp); + + case THUNK_1_0: + case THUNK_0_1: + return copy(q,sizeofW(StgThunk)+1,stp); + + case THUNK_1_1: + case THUNK_2_0: + case THUNK_0_2: +#ifdef NO_PROMOTE_THUNKS + if (bd->gen_no == 0 && + bd->step->no != 0 && + bd->step->no == generations[bd->gen_no].n_steps-1) { + stp = bd->step; + } +#endif + return copy(q,sizeofW(StgThunk)+2,stp); + + case FUN_1_1: + case FUN_2_0: + case CONSTR_1_1: + case CONSTR_2_0: + case FUN_0_2: + return copy(q,sizeofW(StgHeader)+2,stp); + + case CONSTR_0_2: + return copy_noscav(q,sizeofW(StgHeader)+2,stp); + + case THUNK: + return copy(q,thunk_sizeW_fromITBL(info),stp); + + case FUN: + case CONSTR: + case IND_PERM: + case IND_OLDGEN_PERM: + case WEAK: + case STABLE_NAME: + return copy(q,sizeW_fromITBL(info),stp); + + case BCO: + return copy(q,bco_sizeW((StgBCO *)q),stp); + + case CAF_BLACKHOLE: + case SE_CAF_BLACKHOLE: + case SE_BLACKHOLE: + case BLACKHOLE: + return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp); + + case THUNK_SELECTOR: + { + StgClosure *p; + const StgInfoTable *info_ptr; + + if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) { + return copy(q,THUNK_SELECTOR_sizeW(),stp); + } + + // stashed away for LDV profiling, see below + info_ptr = q->header.info; + + p = eval_thunk_selector(info->layout.selector_offset, + (StgSelector *)q); + + if (p == NULL) { + return copy(q,THUNK_SELECTOR_sizeW(),stp); + } else { + StgClosure *val; + // q is still BLACKHOLE'd. + thunk_selector_depth++; + val = evacuate(p); + thunk_selector_depth--; + +#ifdef PROFILING + // For the purposes of LDV profiling, we have destroyed + // the original selector thunk. + SET_INFO(q, info_ptr); + LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(q); +#endif + + // Update the THUNK_SELECTOR with an indirection to the + // EVACUATED closure now at p. Why do this rather than + // upd_evacuee(q,p)? Because we have an invariant that an + // EVACUATED closure always points to an object in the + // same or an older generation (required by the short-cut + // test in the EVACUATED case, below). + SET_INFO(q, &stg_IND_info); + ((StgInd *)q)->indirectee = p; + + // For the purposes of LDV profiling, we have created an + // indirection. + LDV_RECORD_CREATE(q); + + return val; + } + } + + case IND: + case IND_OLDGEN: + // follow chains of indirections, don't evacuate them + q = ((StgInd*)q)->indirectee; + goto loop; + + case RET_BCO: + case RET_SMALL: + case RET_VEC_SMALL: + case RET_BIG: + case RET_VEC_BIG: + case RET_DYN: + case UPDATE_FRAME: + case STOP_FRAME: + case CATCH_FRAME: + case CATCH_STM_FRAME: + case CATCH_RETRY_FRAME: + case ATOMICALLY_FRAME: + // shouldn't see these + barf("evacuate: stack frame at %p\n", q); + + case PAP: + return copy(q,pap_sizeW((StgPAP*)q),stp); + + case AP: + return copy(q,ap_sizeW((StgAP*)q),stp); + + case AP_STACK: + return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp); + + case EVACUATED: + /* Already evacuated, just return the forwarding address. + * HOWEVER: if the requested destination generation (evac_gen) is + * older than the actual generation (because the object was + * already evacuated to a younger generation) then we have to + * set the failed_to_evac flag to indicate that we couldn't + * manage to promote the object to the desired generation. + */ + /* + * Optimisation: the check is fairly expensive, but we can often + * shortcut it if either the required generation is 0, or the + * current object (the EVACUATED) is in a high enough generation. + * We know that an EVACUATED always points to an object in the + * same or an older generation. stp is the lowest step that the + * current object would be evacuated to, so we only do the full + * check if stp is too low. + */ + if (evac_gen > 0 && stp->gen_no < evac_gen) { // optimisation + StgClosure *p = ((StgEvacuated*)q)->evacuee; + if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) { + failed_to_evac = rtsTrue; + TICK_GC_FAILED_PROMOTION(); + } + } + return ((StgEvacuated*)q)->evacuee; + + case ARR_WORDS: + // just copy the block + return copy_noscav(q,arr_words_sizeW((StgArrWords *)q),stp); + + case MUT_ARR_PTRS_CLEAN: + case MUT_ARR_PTRS_DIRTY: + case MUT_ARR_PTRS_FROZEN: + case MUT_ARR_PTRS_FROZEN0: + // just copy the block + return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp); + + case TSO: + { + StgTSO *tso = (StgTSO *)q; + + /* Deal with redirected TSOs (a TSO that's had its stack enlarged). + */ + if (tso->what_next == ThreadRelocated) { + q = (StgClosure *)tso->link; + goto loop; + } + + /* To evacuate a small TSO, we need to relocate the update frame + * list it contains. + */ + { + StgTSO *new_tso; + StgPtr p, q; + + new_tso = (StgTSO *)copyPart((StgClosure *)tso, + tso_sizeW(tso), + sizeofW(StgTSO), stp); + move_TSO(tso, new_tso); + for (p = tso->sp, q = new_tso->sp; + p < tso->stack+tso->stack_size;) { + *q++ = *p++; + } + + return (StgClosure *)new_tso; + } + } + +#if defined(PAR) + case RBH: + { + //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str); + to = copy(q,BLACKHOLE_sizeW(),stp); + //ToDo: derive size etc from reverted IP + //to = copy(q,size,stp); + IF_DEBUG(gc, + debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)", + q, info_type(q), to, info_type(to))); + return to; + } + + case BLOCKED_FETCH: + ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOD_SIZE); + to = copy(q,sizeofW(StgBlockedFetch),stp); + IF_DEBUG(gc, + debugBelch("@@ evacuate: %p (%s) to %p (%s)", + q, info_type(q), to, info_type(to))); + return to; + +# ifdef DIST + case REMOTE_REF: +# endif + case FETCH_ME: + ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOAD_SIZE); + to = copy(q,sizeofW(StgFetchMe),stp); + IF_DEBUG(gc, + debugBelch("@@ evacuate: %p (%s) to %p (%s)", + q, info_type(q), to, info_type(to))); + return to; + + case FETCH_ME_BQ: + ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOAD_SIZE); + to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp); + IF_DEBUG(gc, + debugBelch("@@ evacuate: %p (%s) to %p (%s)", + q, info_type(q), to, info_type(to))); + return to; +#endif + + case TREC_HEADER: + return copy(q,sizeofW(StgTRecHeader),stp); + + case TVAR_WAIT_QUEUE: + return copy(q,sizeofW(StgTVarWaitQueue),stp); + + case TVAR: + return copy(q,sizeofW(StgTVar),stp); + + case TREC_CHUNK: + return copy(q,sizeofW(StgTRecChunk),stp); + + default: + barf("evacuate: strange closure type %d", (int)(info->type)); + } + + barf("evacuate"); +} + +/* ----------------------------------------------------------------------------- + Evaluate a THUNK_SELECTOR if possible. + + returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or + a closure pointer if we evaluated it and this is the result. Note + that "evaluating" the THUNK_SELECTOR doesn't necessarily mean + reducing it to HNF, just that we have eliminated the selection. + The result might be another thunk, or even another THUNK_SELECTOR. + + If the return value is non-NULL, the original selector thunk has + been BLACKHOLE'd, and should be updated with an indirection or a + forwarding pointer. If the return value is NULL, then the selector + thunk is unchanged. + + *** + ToDo: the treatment of THUNK_SELECTORS could be improved in the + following way (from a suggestion by Ian Lynagh): + + We can have a chain like this: + + sel_0 --> (a,b) + | + |-----> sel_0 --> (a,b) + | + |-----> sel_0 --> ... + + and the depth limit means we don't go all the way to the end of the + chain, which results in a space leak. This affects the recursive + call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not* + the recursive call to eval_thunk_selector() in + eval_thunk_selector(). + + We could eliminate the depth bound in this case, in the following + way: + + - traverse the chain once to discover the *value* of the + THUNK_SELECTOR. Mark all THUNK_SELECTORS that we + visit on the way as having been visited already (somehow). + + - in a second pass, traverse the chain again updating all + THUNK_SEELCTORS that we find on the way with indirections to + the value. + + - if we encounter a "marked" THUNK_SELECTOR in a normal + evacuate(), we konw it can't be updated so just evac it. + + Program that illustrates the problem: + + foo [] = ([], []) + foo (x:xs) = let (ys, zs) = foo xs + in if x >= 0 then (x:ys, zs) else (ys, x:zs) + + main = bar [1..(100000000::Int)] + bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs) + + -------------------------------------------------------------------------- */ + +static inline rtsBool +is_to_space ( StgClosure *p ) +{ + bdescr *bd; + + bd = Bdescr((StgPtr)p); + if (HEAP_ALLOCED(p) && + ((bd->flags & BF_EVACUATED) + || ((bd->flags & BF_COMPACTED) && + is_marked((P_)p,bd)))) { + return rtsTrue; + } else { + return rtsFalse; + } +} + +static StgClosure * +eval_thunk_selector( nat field, StgSelector * p ) +{ + StgInfoTable *info; + const StgInfoTable *info_ptr; + StgClosure *selectee; + + selectee = p->selectee; + + // Save the real info pointer (NOTE: not the same as get_itbl()). + info_ptr = p->header.info; + + // If the THUNK_SELECTOR is in a generation that we are not + // collecting, then bail out early. We won't be able to save any + // space in any case, and updating with an indirection is trickier + // in an old gen. + if (Bdescr((StgPtr)p)->gen_no > N) { + return NULL; + } + + // BLACKHOLE the selector thunk, since it is now under evaluation. + // This is important to stop us going into an infinite loop if + // this selector thunk eventually refers to itself. + SET_INFO(p,&stg_BLACKHOLE_info); + +selector_loop: + + // We don't want to end up in to-space, because this causes + // problems when the GC later tries to evacuate the result of + // eval_thunk_selector(). There are various ways this could + // happen: + // + // 1. following an IND_STATIC + // + // 2. when the old generation is compacted, the mark phase updates + // from-space pointers to be to-space pointers, and we can't + // reliably tell which we're following (eg. from an IND_STATIC). + // + // 3. compacting GC again: if we're looking at a constructor in + // the compacted generation, it might point directly to objects + // in to-space. We must bale out here, otherwise doing the selection + // will result in a to-space pointer being returned. + // + // (1) is dealt with using a BF_EVACUATED test on the + // selectee. (2) and (3): we can tell if we're looking at an + // object in the compacted generation that might point to + // to-space objects by testing that (a) it is BF_COMPACTED, (b) + // the compacted generation is being collected, and (c) the + // object is marked. Only a marked object may have pointers that + // point to to-space objects, because that happens when + // scavenging. + // + // The to-space test is now embodied in the in_to_space() inline + // function, as it is re-used below. + // + if (is_to_space(selectee)) { + goto bale_out; + } + + info = get_itbl(selectee); + switch (info->type) { + case CONSTR: + case CONSTR_1_0: + case CONSTR_0_1: + case CONSTR_2_0: + case CONSTR_1_1: + case CONSTR_0_2: + case CONSTR_STATIC: + case CONSTR_NOCAF_STATIC: + // check that the size is in range + ASSERT(field < (StgWord32)(info->layout.payload.ptrs + + info->layout.payload.nptrs)); + + // Select the right field from the constructor, and check + // that the result isn't in to-space. It might be in + // to-space if, for example, this constructor contains + // pointers to younger-gen objects (and is on the mut-once + // list). + // + { + StgClosure *q; + q = selectee->payload[field]; + if (is_to_space(q)) { + goto bale_out; + } else { + return q; + } + } + + case IND: + case IND_PERM: + case IND_OLDGEN: + case IND_OLDGEN_PERM: + case IND_STATIC: + selectee = ((StgInd *)selectee)->indirectee; + goto selector_loop; + + case EVACUATED: + // We don't follow pointers into to-space; the constructor + // has already been evacuated, so we won't save any space + // leaks by evaluating this selector thunk anyhow. + break; + + case THUNK_SELECTOR: + { + StgClosure *val; + + // check that we don't recurse too much, re-using the + // depth bound also used in evacuate(). + if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) { + break; + } + thunk_selector_depth++; + + val = eval_thunk_selector(info->layout.selector_offset, + (StgSelector *)selectee); + + thunk_selector_depth--; + + if (val == NULL) { + break; + } else { + // We evaluated this selector thunk, so update it with + // an indirection. NOTE: we don't use UPD_IND here, + // because we are guaranteed that p is in a generation + // that we are collecting, and we never want to put the + // indirection on a mutable list. +#ifdef PROFILING + // For the purposes of LDV profiling, we have destroyed + // the original selector thunk. + SET_INFO(p, info_ptr); + LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee); +#endif + ((StgInd *)selectee)->indirectee = val; + SET_INFO(selectee,&stg_IND_info); + + // For the purposes of LDV profiling, we have created an + // indirection. + LDV_RECORD_CREATE(selectee); + + selectee = val; + goto selector_loop; + } + } + + case AP: + case AP_STACK: + case THUNK: + case THUNK_1_0: + case THUNK_0_1: + case THUNK_2_0: + case THUNK_1_1: + case THUNK_0_2: + case THUNK_STATIC: + case CAF_BLACKHOLE: + case SE_CAF_BLACKHOLE: + case SE_BLACKHOLE: + case BLACKHOLE: +#if defined(PAR) + case RBH: + case BLOCKED_FETCH: +# ifdef DIST + case REMOTE_REF: +# endif + case FETCH_ME: + case FETCH_ME_BQ: +#endif + // not evaluated yet + break; + + default: + barf("eval_thunk_selector: strange selectee %d", + (int)(info->type)); + } + +bale_out: + // We didn't manage to evaluate this thunk; restore the old info pointer + SET_INFO(p, info_ptr); + return NULL; +} + +/* ----------------------------------------------------------------------------- + move_TSO is called to update the TSO structure after it has been + moved from one place to another. + -------------------------------------------------------------------------- */ + +void +move_TSO (StgTSO *src, StgTSO *dest) +{ + ptrdiff_t diff; + + // relocate the stack pointer... + diff = (StgPtr)dest - (StgPtr)src; // In *words* + dest->sp = (StgPtr)dest->sp + diff; +} + +/* Similar to scavenge_large_bitmap(), but we don't write back the + * pointers we get back from evacuate(). + */ +static void +scavenge_large_srt_bitmap( StgLargeSRT *large_srt ) +{ + nat i, b, size; + StgWord bitmap; + StgClosure **p; + + b = 0; + bitmap = large_srt->l.bitmap[b]; + size = (nat)large_srt->l.size; + p = (StgClosure **)large_srt->srt; + for (i = 0; i < size; ) { + if ((bitmap & 1) != 0) { + evacuate(*p); + } + i++; + p++; + if (i % BITS_IN(W_) == 0) { + b++; + bitmap = large_srt->l.bitmap[b]; + } else { + bitmap = bitmap >> 1; + } + } +} + +/* evacuate the SRT. If srt_bitmap is zero, then there isn't an + * srt field in the info table. That's ok, because we'll + * never dereference it. + */ +STATIC_INLINE void +scavenge_srt (StgClosure **srt, nat srt_bitmap) +{ + nat bitmap; + StgClosure **p; + + bitmap = srt_bitmap; + p = srt; + + if (bitmap == (StgHalfWord)(-1)) { + scavenge_large_srt_bitmap( (StgLargeSRT *)srt ); + return; + } + + while (bitmap != 0) { + if ((bitmap & 1) != 0) { +#ifdef ENABLE_WIN32_DLL_SUPPORT + // Special-case to handle references to closures hiding out in DLLs, since + // double indirections required to get at those. The code generator knows + // which is which when generating the SRT, so it stores the (indirect) + // reference to the DLL closure in the table by first adding one to it. + // We check for this here, and undo the addition before evacuating it. + // + // If the SRT entry hasn't got bit 0 set, the SRT entry points to a + // closure that's fixed at link-time, and no extra magic is required. + if ( (unsigned long)(*srt) & 0x1 ) { + evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1))); + } else { + evacuate(*p); + } +#else + evacuate(*p); +#endif + } + p++; + bitmap = bitmap >> 1; + } +} + + +STATIC_INLINE void +scavenge_thunk_srt(const StgInfoTable *info) +{ + StgThunkInfoTable *thunk_info; + + if (!major_gc) return; + + thunk_info = itbl_to_thunk_itbl(info); + scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap); +} + +STATIC_INLINE void +scavenge_fun_srt(const StgInfoTable *info) +{ + StgFunInfoTable *fun_info; + + if (!major_gc) return; + + fun_info = itbl_to_fun_itbl(info); + scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap); +} + +/* ----------------------------------------------------------------------------- + Scavenge a TSO. + -------------------------------------------------------------------------- */ + +static void +scavengeTSO (StgTSO *tso) +{ + if ( tso->why_blocked == BlockedOnMVar + || tso->why_blocked == BlockedOnBlackHole + || tso->why_blocked == BlockedOnException +#if defined(PAR) + || tso->why_blocked == BlockedOnGA + || tso->why_blocked == BlockedOnGA_NoSend +#endif + ) { + tso->block_info.closure = evacuate(tso->block_info.closure); + } + if ( tso->blocked_exceptions != NULL ) { + tso->blocked_exceptions = + (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions); + } + + // We don't always chase the link field: TSOs on the blackhole + // queue are not automatically alive, so the link field is a + // "weak" pointer in that case. + if (tso->why_blocked != BlockedOnBlackHole) { + tso->link = (StgTSO *)evacuate((StgClosure *)tso->link); + } + + // scavange current transaction record + tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec); + + // scavenge this thread's stack + scavenge_stack(tso->sp, &(tso->stack[tso->stack_size])); +} + +/* ----------------------------------------------------------------------------- + Blocks of function args occur on the stack (at the top) and + in PAPs. + -------------------------------------------------------------------------- */ + +STATIC_INLINE StgPtr +scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args) +{ + StgPtr p; + StgWord bitmap; + nat size; + + p = (StgPtr)args; + switch (fun_info->f.fun_type) { + case ARG_GEN: + bitmap = BITMAP_BITS(fun_info->f.b.bitmap); + size = BITMAP_SIZE(fun_info->f.b.bitmap); + goto small_bitmap; + case ARG_GEN_BIG: + size = GET_FUN_LARGE_BITMAP(fun_info)->size; + scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size); + p += size; + break; + default: + bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]); + size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]); + small_bitmap: + while (size > 0) { + if ((bitmap & 1) == 0) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + p++; + bitmap = bitmap >> 1; + size--; + } + break; + } + return p; +} + +STATIC_INLINE StgPtr +scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size) +{ + StgPtr p; + StgWord bitmap; + StgFunInfoTable *fun_info; + + fun_info = get_fun_itbl(fun); + ASSERT(fun_info->i.type != PAP); + p = (StgPtr)payload; + + switch (fun_info->f.fun_type) { + case ARG_GEN: + bitmap = BITMAP_BITS(fun_info->f.b.bitmap); + goto small_bitmap; + case ARG_GEN_BIG: + scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size); + p += size; + break; + case ARG_BCO: + scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size); + p += size; + break; + default: + bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]); + small_bitmap: + while (size > 0) { + if ((bitmap & 1) == 0) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + p++; + bitmap = bitmap >> 1; + size--; + } + break; + } + return p; +} + +STATIC_INLINE StgPtr +scavenge_PAP (StgPAP *pap) +{ + pap->fun = evacuate(pap->fun); + return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args); +} + +STATIC_INLINE StgPtr +scavenge_AP (StgAP *ap) +{ + ap->fun = evacuate(ap->fun); + return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args); +} + +/* ----------------------------------------------------------------------------- + Scavenge a given step until there are no more objects in this step + to scavenge. + + evac_gen is set by the caller to be either zero (for a step in a + generation < N) or G where G is the generation of the step being + scavenged. + + We sometimes temporarily change evac_gen back to zero if we're + scavenging a mutable object where early promotion isn't such a good + idea. + -------------------------------------------------------------------------- */ + +static void +scavenge(step *stp) +{ + StgPtr p, q; + StgInfoTable *info; + bdescr *bd; + nat saved_evac_gen = evac_gen; + + p = stp->scan; + bd = stp->scan_bd; + + failed_to_evac = rtsFalse; + + /* scavenge phase - standard breadth-first scavenging of the + * evacuated objects + */ + + while (bd != stp->hp_bd || p < stp->hp) { + + // If we're at the end of this block, move on to the next block + if (bd != stp->hp_bd && p == bd->free) { + bd = bd->link; + p = bd->start; + continue; + } + + ASSERT(LOOKS_LIKE_CLOSURE_PTR(p)); + info = get_itbl((StgClosure *)p); + + ASSERT(thunk_selector_depth == 0); + + q = p; + switch (info->type) { + + case MVAR: + { + StgMVar *mvar = ((StgMVar *)p); + evac_gen = 0; + mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head); + mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail); + mvar->value = evacuate((StgClosure *)mvar->value); + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable. + p += sizeofW(StgMVar); + break; + } + + case FUN_2_0: + scavenge_fun_srt(info); + ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]); + ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]); + p += sizeofW(StgHeader) + 2; + break; + + case THUNK_2_0: + scavenge_thunk_srt(info); + ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]); + ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]); + p += sizeofW(StgThunk) + 2; + break; + + case CONSTR_2_0: + ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]); + ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]); + p += sizeofW(StgHeader) + 2; + break; + + case THUNK_1_0: + scavenge_thunk_srt(info); + ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]); + p += sizeofW(StgThunk) + 1; + break; + + case FUN_1_0: + scavenge_fun_srt(info); + case CONSTR_1_0: + ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]); + p += sizeofW(StgHeader) + 1; + break; + + case THUNK_0_1: + scavenge_thunk_srt(info); + p += sizeofW(StgThunk) + 1; + break; + + case FUN_0_1: + scavenge_fun_srt(info); + case CONSTR_0_1: + p += sizeofW(StgHeader) + 1; + break; + + case THUNK_0_2: + scavenge_thunk_srt(info); + p += sizeofW(StgThunk) + 2; + break; + + case FUN_0_2: + scavenge_fun_srt(info); + case CONSTR_0_2: + p += sizeofW(StgHeader) + 2; + break; + + case THUNK_1_1: + scavenge_thunk_srt(info); + ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]); + p += sizeofW(StgThunk) + 2; + break; + + case FUN_1_1: + scavenge_fun_srt(info); + case CONSTR_1_1: + ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]); + p += sizeofW(StgHeader) + 2; + break; + + case FUN: + scavenge_fun_srt(info); + goto gen_obj; + + case THUNK: + { + StgPtr end; + + scavenge_thunk_srt(info); + end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs; + for (p = (P_)((StgThunk *)p)->payload; p < end; p++) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + p += info->layout.payload.nptrs; + break; + } + + gen_obj: + case CONSTR: + case WEAK: + case STABLE_NAME: + { + StgPtr end; + + end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs; + for (p = (P_)((StgClosure *)p)->payload; p < end; p++) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + p += info->layout.payload.nptrs; + break; + } + + case BCO: { + StgBCO *bco = (StgBCO *)p; + bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs); + bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals); + bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs); + bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls); + p += bco_sizeW(bco); + break; + } + + case IND_PERM: + if (stp->gen->no != 0) { +#ifdef PROFILING + // @LDV profiling + // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an + // IND_OLDGEN_PERM closure is larger than an IND_PERM closure. + LDV_recordDead((StgClosure *)p, sizeofW(StgInd)); +#endif + // + // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()? + // + SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info); + + // We pretend that p has just been created. + LDV_RECORD_CREATE((StgClosure *)p); + } + // fall through + case IND_OLDGEN_PERM: + ((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee); + p += sizeofW(StgInd); + break; + + case MUT_VAR_CLEAN: + case MUT_VAR_DIRTY: { + rtsBool saved_eager_promotion = eager_promotion; + + eager_promotion = rtsFalse; + ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var); + eager_promotion = saved_eager_promotion; + + if (failed_to_evac) { + ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info; + } else { + ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info; + } + p += sizeofW(StgMutVar); + break; + } + + case CAF_BLACKHOLE: + case SE_CAF_BLACKHOLE: + case SE_BLACKHOLE: + case BLACKHOLE: + p += BLACKHOLE_sizeW(); + break; + + case THUNK_SELECTOR: + { + StgSelector *s = (StgSelector *)p; + s->selectee = evacuate(s->selectee); + p += THUNK_SELECTOR_sizeW(); + break; + } + + // A chunk of stack saved in a heap object + case AP_STACK: + { + StgAP_STACK *ap = (StgAP_STACK *)p; + + ap->fun = evacuate(ap->fun); + scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size); + p = (StgPtr)ap->payload + ap->size; + break; + } + + case PAP: + p = scavenge_PAP((StgPAP *)p); + break; + + case AP: + p = scavenge_AP((StgAP *)p); + break; + + case ARR_WORDS: + // nothing to follow + p += arr_words_sizeW((StgArrWords *)p); + break; + + case MUT_ARR_PTRS_CLEAN: + case MUT_ARR_PTRS_DIRTY: + // follow everything + { + StgPtr next; + rtsBool saved_eager; + + // We don't eagerly promote objects pointed to by a mutable + // array, but if we find the array only points to objects in + // the same or an older generation, we mark it "clean" and + // avoid traversing it during minor GCs. + saved_eager = eager_promotion; + eager_promotion = rtsFalse; + next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p); + for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + eager_promotion = saved_eager; + + if (failed_to_evac) { + ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info; + } else { + ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info; + } + + failed_to_evac = rtsTrue; // always put it on the mutable list. + break; + } + + case MUT_ARR_PTRS_FROZEN: + case MUT_ARR_PTRS_FROZEN0: + // follow everything + { + StgPtr next; + + next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p); + for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + + // If we're going to put this object on the mutable list, then + // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that. + if (failed_to_evac) { + ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info; + } else { + ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info; + } + break; + } + + case TSO: + { + StgTSO *tso = (StgTSO *)p; + rtsBool saved_eager = eager_promotion; + + eager_promotion = rtsFalse; + scavengeTSO(tso); + eager_promotion = saved_eager; + + if (failed_to_evac) { + tso->flags |= TSO_DIRTY; + } else { + tso->flags &= ~TSO_DIRTY; + } + + failed_to_evac = rtsTrue; // always on the mutable list + p += tso_sizeW(tso); + break; + } + +#if defined(PAR) + case RBH: + { +#if 0 + nat size, ptrs, nonptrs, vhs; + char str[80]; + StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str); +#endif + StgRBH *rbh = (StgRBH *)p; + (StgClosure *)rbh->blocking_queue = + evacuate((StgClosure *)rbh->blocking_queue); + failed_to_evac = rtsTrue; // mutable anyhow. + IF_DEBUG(gc, + debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)", + p, info_type(p), (StgClosure *)rbh->blocking_queue)); + // ToDo: use size of reverted closure here! + p += BLACKHOLE_sizeW(); + break; + } + + case BLOCKED_FETCH: + { + StgBlockedFetch *bf = (StgBlockedFetch *)p; + // follow the pointer to the node which is being demanded + (StgClosure *)bf->node = + evacuate((StgClosure *)bf->node); + // follow the link to the rest of the blocking queue + (StgClosure *)bf->link = + evacuate((StgClosure *)bf->link); + IF_DEBUG(gc, + debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it", + bf, info_type((StgClosure *)bf), + bf->node, info_type(bf->node))); + p += sizeofW(StgBlockedFetch); + break; + } + +#ifdef DIST + case REMOTE_REF: +#endif + case FETCH_ME: + p += sizeofW(StgFetchMe); + break; // nothing to do in this case + + case FETCH_ME_BQ: + { + StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p; + (StgClosure *)fmbq->blocking_queue = + evacuate((StgClosure *)fmbq->blocking_queue); + IF_DEBUG(gc, + debugBelch("@@ scavenge: %p (%s) exciting, isn't it", + p, info_type((StgClosure *)p))); + p += sizeofW(StgFetchMeBlockingQueue); + break; + } +#endif + + case TVAR_WAIT_QUEUE: + { + StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p); + evac_gen = 0; + wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso); + wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry); + wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry); + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable + p += sizeofW(StgTVarWaitQueue); + break; + } + + case TVAR: + { + StgTVar *tvar = ((StgTVar *) p); + evac_gen = 0; + tvar->current_value = evacuate((StgClosure*)tvar->current_value); + tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry); + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable + p += sizeofW(StgTVar); + break; + } + + case TREC_HEADER: + { + StgTRecHeader *trec = ((StgTRecHeader *) p); + evac_gen = 0; + trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec); + trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk); + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable + p += sizeofW(StgTRecHeader); + break; + } + + case TREC_CHUNK: + { + StgWord i; + StgTRecChunk *tc = ((StgTRecChunk *) p); + TRecEntry *e = &(tc -> entries[0]); + evac_gen = 0; + tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk); + for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) { + e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar); + e->expected_value = evacuate((StgClosure*)e->expected_value); + e->new_value = evacuate((StgClosure*)e->new_value); + } + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable + p += sizeofW(StgTRecChunk); + break; + } + + default: + barf("scavenge: unimplemented/strange closure type %d @ %p", + info->type, p); + } + + /* + * We need to record the current object on the mutable list if + * (a) It is actually mutable, or + * (b) It contains pointers to a younger generation. + * Case (b) arises if we didn't manage to promote everything that + * the current object points to into the current generation. + */ + if (failed_to_evac) { + failed_to_evac = rtsFalse; + if (stp->gen_no > 0) { + recordMutableGen((StgClosure *)q, stp->gen); + } + } + } + + stp->scan_bd = bd; + stp->scan = p; +} + +/* ----------------------------------------------------------------------------- + Scavenge everything on the mark stack. + + This is slightly different from scavenge(): + - we don't walk linearly through the objects, so the scavenger + doesn't need to advance the pointer on to the next object. + -------------------------------------------------------------------------- */ + +static void +scavenge_mark_stack(void) +{ + StgPtr p, q; + StgInfoTable *info; + nat saved_evac_gen; + + evac_gen = oldest_gen->no; + saved_evac_gen = evac_gen; + +linear_scan: + while (!mark_stack_empty()) { + p = pop_mark_stack(); + + ASSERT(LOOKS_LIKE_CLOSURE_PTR(p)); + info = get_itbl((StgClosure *)p); + + q = p; + switch (info->type) { + + case MVAR: + { + StgMVar *mvar = ((StgMVar *)p); + evac_gen = 0; + mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head); + mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail); + mvar->value = evacuate((StgClosure *)mvar->value); + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable. + break; + } + + case FUN_2_0: + scavenge_fun_srt(info); + ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]); + ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]); + break; + + case THUNK_2_0: + scavenge_thunk_srt(info); + ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]); + ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]); + break; + + case CONSTR_2_0: + ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]); + ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]); + break; + + case FUN_1_0: + case FUN_1_1: + scavenge_fun_srt(info); + ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]); + break; + + case THUNK_1_0: + case THUNK_1_1: + scavenge_thunk_srt(info); + ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]); + break; + + case CONSTR_1_0: + case CONSTR_1_1: + ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]); + break; + + case FUN_0_1: + case FUN_0_2: + scavenge_fun_srt(info); + break; + + case THUNK_0_1: + case THUNK_0_2: + scavenge_thunk_srt(info); + break; + + case CONSTR_0_1: + case CONSTR_0_2: + break; + + case FUN: + scavenge_fun_srt(info); + goto gen_obj; + + case THUNK: + { + StgPtr end; + + scavenge_thunk_srt(info); + end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs; + for (p = (P_)((StgThunk *)p)->payload; p < end; p++) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + break; + } + + gen_obj: + case CONSTR: + case WEAK: + case STABLE_NAME: + { + StgPtr end; + + end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs; + for (p = (P_)((StgClosure *)p)->payload; p < end; p++) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + break; + } + + case BCO: { + StgBCO *bco = (StgBCO *)p; + bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs); + bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals); + bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs); + bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls); + break; + } + + case IND_PERM: + // don't need to do anything here: the only possible case + // is that we're in a 1-space compacting collector, with + // no "old" generation. + break; + + case IND_OLDGEN: + case IND_OLDGEN_PERM: + ((StgInd *)p)->indirectee = + evacuate(((StgInd *)p)->indirectee); + break; + + case MUT_VAR_CLEAN: + case MUT_VAR_DIRTY: { + rtsBool saved_eager_promotion = eager_promotion; + + eager_promotion = rtsFalse; + ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var); + eager_promotion = saved_eager_promotion; + + if (failed_to_evac) { + ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info; + } else { + ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info; + } + break; + } + + case CAF_BLACKHOLE: + case SE_CAF_BLACKHOLE: + case SE_BLACKHOLE: + case BLACKHOLE: + case ARR_WORDS: + break; + + case THUNK_SELECTOR: + { + StgSelector *s = (StgSelector *)p; + s->selectee = evacuate(s->selectee); + break; + } + + // A chunk of stack saved in a heap object + case AP_STACK: + { + StgAP_STACK *ap = (StgAP_STACK *)p; + + ap->fun = evacuate(ap->fun); + scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size); + break; + } + + case PAP: + scavenge_PAP((StgPAP *)p); + break; + + case AP: + scavenge_AP((StgAP *)p); + break; + + case MUT_ARR_PTRS_CLEAN: + case MUT_ARR_PTRS_DIRTY: + // follow everything + { + StgPtr next; + rtsBool saved_eager; + + // We don't eagerly promote objects pointed to by a mutable + // array, but if we find the array only points to objects in + // the same or an older generation, we mark it "clean" and + // avoid traversing it during minor GCs. + saved_eager = eager_promotion; + eager_promotion = rtsFalse; + next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p); + for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + eager_promotion = saved_eager; + + if (failed_to_evac) { + ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info; + } else { + ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info; + } + + failed_to_evac = rtsTrue; // mutable anyhow. + break; + } + + case MUT_ARR_PTRS_FROZEN: + case MUT_ARR_PTRS_FROZEN0: + // follow everything + { + StgPtr next, q = p; + + next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p); + for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + + // If we're going to put this object on the mutable list, then + // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that. + if (failed_to_evac) { + ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info; + } else { + ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info; + } + break; + } + + case TSO: + { + StgTSO *tso = (StgTSO *)p; + rtsBool saved_eager = eager_promotion; + + eager_promotion = rtsFalse; + scavengeTSO(tso); + eager_promotion = saved_eager; + + if (failed_to_evac) { + tso->flags |= TSO_DIRTY; + } else { + tso->flags &= ~TSO_DIRTY; + } + + failed_to_evac = rtsTrue; // always on the mutable list + break; + } + +#if defined(PAR) + case RBH: + { +#if 0 + nat size, ptrs, nonptrs, vhs; + char str[80]; + StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str); +#endif + StgRBH *rbh = (StgRBH *)p; + bh->blocking_queue = + (StgTSO *)evacuate((StgClosure *)bh->blocking_queue); + failed_to_evac = rtsTrue; // mutable anyhow. + IF_DEBUG(gc, + debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)", + p, info_type(p), (StgClosure *)rbh->blocking_queue)); + break; + } + + case BLOCKED_FETCH: + { + StgBlockedFetch *bf = (StgBlockedFetch *)p; + // follow the pointer to the node which is being demanded + (StgClosure *)bf->node = + evacuate((StgClosure *)bf->node); + // follow the link to the rest of the blocking queue + (StgClosure *)bf->link = + evacuate((StgClosure *)bf->link); + IF_DEBUG(gc, + debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it", + bf, info_type((StgClosure *)bf), + bf->node, info_type(bf->node))); + break; + } + +#ifdef DIST + case REMOTE_REF: +#endif + case FETCH_ME: + break; // nothing to do in this case + + case FETCH_ME_BQ: + { + StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p; + (StgClosure *)fmbq->blocking_queue = + evacuate((StgClosure *)fmbq->blocking_queue); + IF_DEBUG(gc, + debugBelch("@@ scavenge: %p (%s) exciting, isn't it", + p, info_type((StgClosure *)p))); + break; + } +#endif /* PAR */ + + case TVAR_WAIT_QUEUE: + { + StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p); + evac_gen = 0; + wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso); + wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry); + wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry); + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable + break; + } + + case TVAR: + { + StgTVar *tvar = ((StgTVar *) p); + evac_gen = 0; + tvar->current_value = evacuate((StgClosure*)tvar->current_value); + tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry); + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable + break; + } + + case TREC_CHUNK: + { + StgWord i; + StgTRecChunk *tc = ((StgTRecChunk *) p); + TRecEntry *e = &(tc -> entries[0]); + evac_gen = 0; + tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk); + for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) { + e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar); + e->expected_value = evacuate((StgClosure*)e->expected_value); + e->new_value = evacuate((StgClosure*)e->new_value); + } + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable + break; + } + + case TREC_HEADER: + { + StgTRecHeader *trec = ((StgTRecHeader *) p); + evac_gen = 0; + trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec); + trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk); + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable + break; + } + + default: + barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p", + info->type, p); + } + + if (failed_to_evac) { + failed_to_evac = rtsFalse; + if (evac_gen > 0) { + recordMutableGen((StgClosure *)q, &generations[evac_gen]); + } + } + + // mark the next bit to indicate "scavenged" + mark(q+1, Bdescr(q)); + + } // while (!mark_stack_empty()) + + // start a new linear scan if the mark stack overflowed at some point + if (mark_stack_overflowed && oldgen_scan_bd == NULL) { + IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan")); + mark_stack_overflowed = rtsFalse; + oldgen_scan_bd = oldest_gen->steps[0].old_blocks; + oldgen_scan = oldgen_scan_bd->start; + } + + if (oldgen_scan_bd) { + // push a new thing on the mark stack + loop: + // find a closure that is marked but not scavenged, and start + // from there. + while (oldgen_scan < oldgen_scan_bd->free + && !is_marked(oldgen_scan,oldgen_scan_bd)) { + oldgen_scan++; + } + + if (oldgen_scan < oldgen_scan_bd->free) { + + // already scavenged? + if (is_marked(oldgen_scan+1,oldgen_scan_bd)) { + oldgen_scan += sizeofW(StgHeader) + MIN_PAYLOAD_SIZE; + goto loop; + } + push_mark_stack(oldgen_scan); + // ToDo: bump the linear scan by the actual size of the object + oldgen_scan += sizeofW(StgHeader) + MIN_PAYLOAD_SIZE; + goto linear_scan; + } + + oldgen_scan_bd = oldgen_scan_bd->link; + if (oldgen_scan_bd != NULL) { + oldgen_scan = oldgen_scan_bd->start; + goto loop; + } + } +} + +/* ----------------------------------------------------------------------------- + Scavenge one object. + + This is used for objects that are temporarily marked as mutable + because they contain old-to-new generation pointers. Only certain + objects can have this property. + -------------------------------------------------------------------------- */ + +static rtsBool +scavenge_one(StgPtr p) +{ + const StgInfoTable *info; + nat saved_evac_gen = evac_gen; + rtsBool no_luck; + + ASSERT(LOOKS_LIKE_CLOSURE_PTR(p)); + info = get_itbl((StgClosure *)p); + + switch (info->type) { + + case MVAR: + { + StgMVar *mvar = ((StgMVar *)p); + evac_gen = 0; + mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head); + mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail); + mvar->value = evacuate((StgClosure *)mvar->value); + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable. + break; + } + + case THUNK: + case THUNK_1_0: + case THUNK_0_1: + case THUNK_1_1: + case THUNK_0_2: + case THUNK_2_0: + { + StgPtr q, end; + + end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs; + for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) { + *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q); + } + break; + } + + case FUN: + case FUN_1_0: // hardly worth specialising these guys + case FUN_0_1: + case FUN_1_1: + case FUN_0_2: + case FUN_2_0: + case CONSTR: + case CONSTR_1_0: + case CONSTR_0_1: + case CONSTR_1_1: + case CONSTR_0_2: + case CONSTR_2_0: + case WEAK: + case IND_PERM: + { + StgPtr q, end; + + end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs; + for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) { + *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q); + } + break; + } + + case MUT_VAR_CLEAN: + case MUT_VAR_DIRTY: { + StgPtr q = p; + rtsBool saved_eager_promotion = eager_promotion; + + eager_promotion = rtsFalse; + ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var); + eager_promotion = saved_eager_promotion; + + if (failed_to_evac) { + ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info; + } else { + ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info; + } + break; + } + + case CAF_BLACKHOLE: + case SE_CAF_BLACKHOLE: + case SE_BLACKHOLE: + case BLACKHOLE: + break; + + case THUNK_SELECTOR: + { + StgSelector *s = (StgSelector *)p; + s->selectee = evacuate(s->selectee); + break; + } + + case AP_STACK: + { + StgAP_STACK *ap = (StgAP_STACK *)p; + + ap->fun = evacuate(ap->fun); + scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size); + p = (StgPtr)ap->payload + ap->size; + break; + } + + case PAP: + p = scavenge_PAP((StgPAP *)p); + break; + + case AP: + p = scavenge_AP((StgAP *)p); + break; + + case ARR_WORDS: + // nothing to follow + break; + + case MUT_ARR_PTRS_CLEAN: + case MUT_ARR_PTRS_DIRTY: + { + StgPtr next, q; + rtsBool saved_eager; + + // We don't eagerly promote objects pointed to by a mutable + // array, but if we find the array only points to objects in + // the same or an older generation, we mark it "clean" and + // avoid traversing it during minor GCs. + saved_eager = eager_promotion; + eager_promotion = rtsFalse; + q = p; + next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p); + for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + eager_promotion = saved_eager; + + if (failed_to_evac) { + ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info; + } else { + ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info; + } + + failed_to_evac = rtsTrue; + break; + } + + case MUT_ARR_PTRS_FROZEN: + case MUT_ARR_PTRS_FROZEN0: + { + // follow everything + StgPtr next, q=p; + + next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p); + for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + + // If we're going to put this object on the mutable list, then + // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that. + if (failed_to_evac) { + ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info; + } else { + ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info; + } + break; + } + + case TSO: + { + StgTSO *tso = (StgTSO *)p; + rtsBool saved_eager = eager_promotion; + + eager_promotion = rtsFalse; + scavengeTSO(tso); + eager_promotion = saved_eager; + + if (failed_to_evac) { + tso->flags |= TSO_DIRTY; + } else { + tso->flags &= ~TSO_DIRTY; + } + + failed_to_evac = rtsTrue; // always on the mutable list + break; + } + +#if defined(PAR) + case RBH: + { +#if 0 + nat size, ptrs, nonptrs, vhs; + char str[80]; + StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str); +#endif + StgRBH *rbh = (StgRBH *)p; + (StgClosure *)rbh->blocking_queue = + evacuate((StgClosure *)rbh->blocking_queue); + failed_to_evac = rtsTrue; // mutable anyhow. + IF_DEBUG(gc, + debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)", + p, info_type(p), (StgClosure *)rbh->blocking_queue)); + // ToDo: use size of reverted closure here! + break; + } + + case BLOCKED_FETCH: + { + StgBlockedFetch *bf = (StgBlockedFetch *)p; + // follow the pointer to the node which is being demanded + (StgClosure *)bf->node = + evacuate((StgClosure *)bf->node); + // follow the link to the rest of the blocking queue + (StgClosure *)bf->link = + evacuate((StgClosure *)bf->link); + IF_DEBUG(gc, + debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it", + bf, info_type((StgClosure *)bf), + bf->node, info_type(bf->node))); + break; + } + +#ifdef DIST + case REMOTE_REF: +#endif + case FETCH_ME: + break; // nothing to do in this case + + case FETCH_ME_BQ: + { + StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p; + (StgClosure *)fmbq->blocking_queue = + evacuate((StgClosure *)fmbq->blocking_queue); + IF_DEBUG(gc, + debugBelch("@@ scavenge: %p (%s) exciting, isn't it", + p, info_type((StgClosure *)p))); + break; + } +#endif + + case TVAR_WAIT_QUEUE: + { + StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p); + evac_gen = 0; + wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso); + wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry); + wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry); + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable + break; + } + + case TVAR: + { + StgTVar *tvar = ((StgTVar *) p); + evac_gen = 0; + tvar->current_value = evacuate((StgClosure*)tvar->current_value); + tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry); + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable + break; + } + + case TREC_HEADER: + { + StgTRecHeader *trec = ((StgTRecHeader *) p); + evac_gen = 0; + trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec); + trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk); + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable + break; + } + + case TREC_CHUNK: + { + StgWord i; + StgTRecChunk *tc = ((StgTRecChunk *) p); + TRecEntry *e = &(tc -> entries[0]); + evac_gen = 0; + tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk); + for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) { + e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar); + e->expected_value = evacuate((StgClosure*)e->expected_value); + e->new_value = evacuate((StgClosure*)e->new_value); + } + evac_gen = saved_evac_gen; + failed_to_evac = rtsTrue; // mutable + break; + } + + case IND_OLDGEN: + case IND_OLDGEN_PERM: + case IND_STATIC: + { + /* Careful here: a THUNK can be on the mutable list because + * it contains pointers to young gen objects. If such a thunk + * is updated, the IND_OLDGEN will be added to the mutable + * list again, and we'll scavenge it twice. evacuate() + * doesn't check whether the object has already been + * evacuated, so we perform that check here. + */ + StgClosure *q = ((StgInd *)p)->indirectee; + if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) { + break; + } + ((StgInd *)p)->indirectee = evacuate(q); + } + +#if 0 && defined(DEBUG) + if (RtsFlags.DebugFlags.gc) + /* Debugging code to print out the size of the thing we just + * promoted + */ + { + StgPtr start = gen->steps[0].scan; + bdescr *start_bd = gen->steps[0].scan_bd; + nat size = 0; + scavenge(&gen->steps[0]); + if (start_bd != gen->steps[0].scan_bd) { + size += (P_)BLOCK_ROUND_UP(start) - start; + start_bd = start_bd->link; + while (start_bd != gen->steps[0].scan_bd) { + size += BLOCK_SIZE_W; + start_bd = start_bd->link; + } + size += gen->steps[0].scan - + (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan); + } else { + size = gen->steps[0].scan - start; + } + debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_)); + } +#endif + break; + + default: + barf("scavenge_one: strange object %d", (int)(info->type)); + } + + no_luck = failed_to_evac; + failed_to_evac = rtsFalse; + return (no_luck); +} + +/* ----------------------------------------------------------------------------- + Scavenging mutable lists. + + We treat the mutable list of each generation > N (i.e. all the + generations older than the one being collected) as roots. We also + remove non-mutable objects from the mutable list at this point. + -------------------------------------------------------------------------- */ + +static void +scavenge_mutable_list(generation *gen) +{ + bdescr *bd; + StgPtr p, q; + + bd = gen->saved_mut_list; + + evac_gen = gen->no; + for (; bd != NULL; bd = bd->link) { + for (q = bd->start; q < bd->free; q++) { + p = (StgPtr)*q; + ASSERT(LOOKS_LIKE_CLOSURE_PTR(p)); + +#ifdef DEBUG + switch (get_itbl((StgClosure *)p)->type) { + case MUT_VAR_CLEAN: + barf("MUT_VAR_CLEAN on mutable list"); + case MUT_VAR_DIRTY: + mutlist_MUTVARS++; break; + case MUT_ARR_PTRS_CLEAN: + case MUT_ARR_PTRS_DIRTY: + case MUT_ARR_PTRS_FROZEN: + case MUT_ARR_PTRS_FROZEN0: + mutlist_MUTARRS++; break; + default: + mutlist_OTHERS++; break; + } +#endif + + // Check whether this object is "clean", that is it + // definitely doesn't point into a young generation. + // Clean objects don't need to be scavenged. Some clean + // objects (MUT_VAR_CLEAN) are not kept on the mutable + // list at all; others, such as MUT_ARR_PTRS_CLEAN and + // TSO, are always on the mutable list. + // + switch (get_itbl((StgClosure *)p)->type) { + case MUT_ARR_PTRS_CLEAN: + recordMutableGen((StgClosure *)p,gen); + continue; + case TSO: { + StgTSO *tso = (StgTSO *)p; + if ((tso->flags & TSO_DIRTY) == 0) { + // A clean TSO: we don't have to traverse its + // stack. However, we *do* follow the link field: + // we don't want to have to mark a TSO dirty just + // because we put it on a different queue. + if (tso->why_blocked != BlockedOnBlackHole) { + tso->link = (StgTSO *)evacuate((StgClosure *)tso->link); + } + recordMutableGen((StgClosure *)p,gen); + continue; + } + } + default: + ; + } + + if (scavenge_one(p)) { + // didn't manage to promote everything, so put the + // object back on the list. + recordMutableGen((StgClosure *)p,gen); + } + } + } + + // free the old mut_list + freeChain(gen->saved_mut_list); + gen->saved_mut_list = NULL; +} + + +static void +scavenge_static(void) +{ + StgClosure* p = static_objects; + const StgInfoTable *info; + + /* Always evacuate straight to the oldest generation for static + * objects */ + evac_gen = oldest_gen->no; + + /* keep going until we've scavenged all the objects on the linked + list... */ + while (p != END_OF_STATIC_LIST) { + + ASSERT(LOOKS_LIKE_CLOSURE_PTR(p)); + info = get_itbl(p); + /* + if (info->type==RBH) + info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure + */ + // make sure the info pointer is into text space + + /* Take this object *off* the static_objects list, + * and put it on the scavenged_static_objects list. + */ + static_objects = *STATIC_LINK(info,p); + *STATIC_LINK(info,p) = scavenged_static_objects; + scavenged_static_objects = p; + + switch (info -> type) { + + case IND_STATIC: + { + StgInd *ind = (StgInd *)p; + ind->indirectee = evacuate(ind->indirectee); + + /* might fail to evacuate it, in which case we have to pop it + * back on the mutable list of the oldest generation. We + * leave it *on* the scavenged_static_objects list, though, + * in case we visit this object again. + */ + if (failed_to_evac) { + failed_to_evac = rtsFalse; + recordMutableGen((StgClosure *)p,oldest_gen); + } + break; + } + + case THUNK_STATIC: + scavenge_thunk_srt(info); + break; + + case FUN_STATIC: + scavenge_fun_srt(info); + break; + + case CONSTR_STATIC: + { + StgPtr q, next; + + next = (P_)p->payload + info->layout.payload.ptrs; + // evacuate the pointers + for (q = (P_)p->payload; q < next; q++) { + *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q); + } + break; + } + + default: + barf("scavenge_static: strange closure %d", (int)(info->type)); + } + + ASSERT(failed_to_evac == rtsFalse); + + /* get the next static object from the list. Remember, there might + * be more stuff on this list now that we've done some evacuating! + * (static_objects is a global) + */ + p = static_objects; + } +} + +/* ----------------------------------------------------------------------------- + scavenge a chunk of memory described by a bitmap + -------------------------------------------------------------------------- */ + +static void +scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size ) +{ + nat i, b; + StgWord bitmap; + + b = 0; + bitmap = large_bitmap->bitmap[b]; + for (i = 0; i < size; ) { + if ((bitmap & 1) == 0) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + i++; + p++; + if (i % BITS_IN(W_) == 0) { + b++; + bitmap = large_bitmap->bitmap[b]; + } else { + bitmap = bitmap >> 1; + } + } +} + +STATIC_INLINE StgPtr +scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap) +{ + while (size > 0) { + if ((bitmap & 1) == 0) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + } + p++; + bitmap = bitmap >> 1; + size--; + } + return p; +} + +/* ----------------------------------------------------------------------------- + scavenge_stack walks over a section of stack and evacuates all the + objects pointed to by it. We can use the same code for walking + AP_STACK_UPDs, since these are just sections of copied stack. + -------------------------------------------------------------------------- */ + + +static void +scavenge_stack(StgPtr p, StgPtr stack_end) +{ + const StgRetInfoTable* info; + StgWord bitmap; + nat size; + + //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end)); + + /* + * Each time around this loop, we are looking at a chunk of stack + * that starts with an activation record. + */ + + while (p < stack_end) { + info = get_ret_itbl((StgClosure *)p); + + switch (info->i.type) { + + case UPDATE_FRAME: + // In SMP, we can get update frames that point to indirections + // when two threads evaluate the same thunk. We do attempt to + // discover this situation in threadPaused(), but it's + // possible that the following sequence occurs: + // + // A B + // enter T + // enter T + // blackhole T + // update T + // GC + // + // Now T is an indirection, and the update frame is already + // marked on A's stack, so we won't traverse it again in + // threadPaused(). We could traverse the whole stack again + // before GC, but that seems like overkill. + // + // Scavenging this update frame as normal would be disastrous; + // the updatee would end up pointing to the value. So we turn + // the indirection into an IND_PERM, so that evacuate will + // copy the indirection into the old generation instead of + // discarding it. + if (get_itbl(((StgUpdateFrame *)p)->updatee)->type == IND) { + ((StgUpdateFrame *)p)->updatee->header.info = + (StgInfoTable *)&stg_IND_PERM_info; + } + ((StgUpdateFrame *)p)->updatee + = evacuate(((StgUpdateFrame *)p)->updatee); + p += sizeofW(StgUpdateFrame); + continue; + + // small bitmap (< 32 entries, or 64 on a 64-bit machine) + case CATCH_STM_FRAME: + case CATCH_RETRY_FRAME: + case ATOMICALLY_FRAME: + case STOP_FRAME: + case CATCH_FRAME: + case RET_SMALL: + case RET_VEC_SMALL: + bitmap = BITMAP_BITS(info->i.layout.bitmap); + size = BITMAP_SIZE(info->i.layout.bitmap); + // NOTE: the payload starts immediately after the info-ptr, we + // don't have an StgHeader in the same sense as a heap closure. + p++; + p = scavenge_small_bitmap(p, size, bitmap); + + follow_srt: + if (major_gc) + scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap); + continue; + + case RET_BCO: { + StgBCO *bco; + nat size; + + p++; + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + bco = (StgBCO *)*p; + p++; + size = BCO_BITMAP_SIZE(bco); + scavenge_large_bitmap(p, BCO_BITMAP(bco), size); + p += size; + continue; + } + + // large bitmap (> 32 entries, or > 64 on a 64-bit machine) + case RET_BIG: + case RET_VEC_BIG: + { + nat size; + + size = GET_LARGE_BITMAP(&info->i)->size; + p++; + scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size); + p += size; + // and don't forget to follow the SRT + goto follow_srt; + } + + // Dynamic bitmap: the mask is stored on the stack, and + // there are a number of non-pointers followed by a number + // of pointers above the bitmapped area. (see StgMacros.h, + // HEAP_CHK_GEN). + case RET_DYN: + { + StgWord dyn; + dyn = ((StgRetDyn *)p)->liveness; + + // traverse the bitmap first + bitmap = RET_DYN_LIVENESS(dyn); + p = (P_)&((StgRetDyn *)p)->payload[0]; + size = RET_DYN_BITMAP_SIZE; + p = scavenge_small_bitmap(p, size, bitmap); + + // skip over the non-ptr words + p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE; + + // follow the ptr words + for (size = RET_DYN_PTRS(dyn); size > 0; size--) { + *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p); + p++; + } + continue; + } + + case RET_FUN: + { + StgRetFun *ret_fun = (StgRetFun *)p; + StgFunInfoTable *fun_info; + + ret_fun->fun = evacuate(ret_fun->fun); + fun_info = get_fun_itbl(ret_fun->fun); + p = scavenge_arg_block(fun_info, ret_fun->payload); + goto follow_srt; + } + + default: + barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type)); + } + } +} + +/*----------------------------------------------------------------------------- + scavenge the large object list. + + evac_gen set by caller; similar games played with evac_gen as with + scavenge() - see comment at the top of scavenge(). Most large + objects are (repeatedly) mutable, so most of the time evac_gen will + be zero. + --------------------------------------------------------------------------- */ + +static void +scavenge_large(step *stp) +{ + bdescr *bd; + StgPtr p; + + bd = stp->new_large_objects; + + for (; bd != NULL; bd = stp->new_large_objects) { + + /* take this object *off* the large objects list and put it on + * the scavenged large objects list. This is so that we can + * treat new_large_objects as a stack and push new objects on + * the front when evacuating. + */ + stp->new_large_objects = bd->link; + dbl_link_onto(bd, &stp->scavenged_large_objects); + + // update the block count in this step. + stp->n_scavenged_large_blocks += bd->blocks; + + p = bd->start; + if (scavenge_one(p)) { + if (stp->gen_no > 0) { + recordMutableGen((StgClosure *)p, stp->gen); + } + } + } +} + +/* ----------------------------------------------------------------------------- + Initialising the static object & mutable lists + -------------------------------------------------------------------------- */ + +static void +zero_static_object_list(StgClosure* first_static) +{ + StgClosure* p; + StgClosure* link; + const StgInfoTable *info; + + for (p = first_static; p != END_OF_STATIC_LIST; p = link) { + info = get_itbl(p); + link = *STATIC_LINK(info, p); + *STATIC_LINK(info,p) = NULL; + } +} + +/* ----------------------------------------------------------------------------- + Reverting CAFs + -------------------------------------------------------------------------- */ + +void +revertCAFs( void ) +{ + StgIndStatic *c; + + for (c = (StgIndStatic *)revertible_caf_list; c != NULL; + c = (StgIndStatic *)c->static_link) + { + SET_INFO(c, c->saved_info); + c->saved_info = NULL; + // could, but not necessary: c->static_link = NULL; + } + revertible_caf_list = NULL; +} + +void +markCAFs( evac_fn evac ) +{ + StgIndStatic *c; + + for (c = (StgIndStatic *)caf_list; c != NULL; + c = (StgIndStatic *)c->static_link) + { + evac(&c->indirectee); + } + for (c = (StgIndStatic *)revertible_caf_list; c != NULL; + c = (StgIndStatic *)c->static_link) + { + evac(&c->indirectee); + } +} + +/* ----------------------------------------------------------------------------- + Sanity code for CAF garbage collection. + + With DEBUG turned on, we manage a CAF list in addition to the SRT + mechanism. After GC, we run down the CAF list and blackhole any + CAFs which have been garbage collected. This means we get an error + whenever the program tries to enter a garbage collected CAF. + + Any garbage collected CAFs are taken off the CAF list at the same + time. + -------------------------------------------------------------------------- */ + +#if 0 && defined(DEBUG) + +static void +gcCAFs(void) +{ + StgClosure* p; + StgClosure** pp; + const StgInfoTable *info; + nat i; + + i = 0; + p = caf_list; + pp = &caf_list; + + while (p != NULL) { + + info = get_itbl(p); + + ASSERT(info->type == IND_STATIC); + + if (STATIC_LINK(info,p) == NULL) { + IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p)); + // black hole it + SET_INFO(p,&stg_BLACKHOLE_info); + p = STATIC_LINK2(info,p); + *pp = p; + } + else { + pp = &STATIC_LINK2(info,p); + p = *pp; + i++; + } + + } + + // debugBelch("%d CAFs live", i); +} +#endif + + +/* ----------------------------------------------------------------------------- + * Stack squeezing + * + * Code largely pinched from old RTS, then hacked to bits. We also do + * lazy black holing here. + * + * -------------------------------------------------------------------------- */ + +struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; }; + +static void +stackSqueeze(StgTSO *tso, StgPtr bottom) +{ + StgPtr frame; + rtsBool prev_was_update_frame; + StgClosure *updatee = NULL; + StgRetInfoTable *info; + StgWord current_gap_size; + struct stack_gap *gap; + + // Stage 1: + // Traverse the stack upwards, replacing adjacent update frames + // with a single update frame and a "stack gap". A stack gap + // contains two values: the size of the gap, and the distance + // to the next gap (or the stack top). + + frame = tso->sp; + + ASSERT(frame < bottom); + + prev_was_update_frame = rtsFalse; + current_gap_size = 0; + gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame)); + + while (frame < bottom) { + + info = get_ret_itbl((StgClosure *)frame); + switch (info->i.type) { + + case UPDATE_FRAME: + { + StgUpdateFrame *upd = (StgUpdateFrame *)frame; + + if (prev_was_update_frame) { + + TICK_UPD_SQUEEZED(); + /* wasn't there something about update squeezing and ticky to be + * sorted out? oh yes: we aren't counting each enter properly + * in this case. See the log somewhere. KSW 1999-04-21 + * + * Check two things: that the two update frames don't point to + * the same object, and that the updatee_bypass isn't already an + * indirection. Both of these cases only happen when we're in a + * block hole-style loop (and there are multiple update frames + * on the stack pointing to the same closure), but they can both + * screw us up if we don't check. + */ + if (upd->updatee != updatee && !closure_IND(upd->updatee)) { + UPD_IND_NOLOCK(upd->updatee, updatee); + } + + // now mark this update frame as a stack gap. The gap + // marker resides in the bottom-most update frame of + // the series of adjacent frames, and covers all the + // frames in this series. + current_gap_size += sizeofW(StgUpdateFrame); + ((struct stack_gap *)frame)->gap_size = current_gap_size; + ((struct stack_gap *)frame)->next_gap = gap; + + frame += sizeofW(StgUpdateFrame); + continue; + } + + // single update frame, or the topmost update frame in a series + else { + prev_was_update_frame = rtsTrue; + updatee = upd->updatee; + frame += sizeofW(StgUpdateFrame); + continue; + } + } + + default: + prev_was_update_frame = rtsFalse; + + // we're not in a gap... check whether this is the end of a gap + // (an update frame can't be the end of a gap). + if (current_gap_size != 0) { + gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame)); + } + current_gap_size = 0; + + frame += stack_frame_sizeW((StgClosure *)frame); + continue; + } + } + + if (current_gap_size != 0) { + gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame)); + } + + // Now we have a stack with gaps in it, and we have to walk down + // shoving the stack up to fill in the gaps. A diagram might + // help: + // + // +| ********* | + // | ********* | <- sp + // | | + // | | <- gap_start + // | ......... | | + // | stack_gap | <- gap | chunk_size + // | ......... | | + // | ......... | <- gap_end v + // | ********* | + // | ********* | + // | ********* | + // -| ********* | + // + // 'sp' points the the current top-of-stack + // 'gap' points to the stack_gap structure inside the gap + // ***** indicates real stack data + // ..... indicates gap + // <empty> indicates unused + // + { + void *sp; + void *gap_start, *next_gap_start, *gap_end; + nat chunk_size; + + next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame)); + sp = next_gap_start; + + while ((StgPtr)gap > tso->sp) { + + // we're working in *bytes* now... + gap_start = next_gap_start; + gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_)); + + gap = gap->next_gap; + next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame)); + + chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start; + sp -= chunk_size; + memmove(sp, next_gap_start, chunk_size); + } + + tso->sp = (StgPtr)sp; + } +} + +/* ----------------------------------------------------------------------------- + * Pausing a thread + * + * We have to prepare for GC - this means doing lazy black holing + * here. We also take the opportunity to do stack squeezing if it's + * turned on. + * -------------------------------------------------------------------------- */ +void +threadPaused(Capability *cap, StgTSO *tso) +{ + StgClosure *frame; + StgRetInfoTable *info; + StgClosure *bh; + StgPtr stack_end; + nat words_to_squeeze = 0; + nat weight = 0; + nat weight_pending = 0; + rtsBool prev_was_update_frame; + + stack_end = &tso->stack[tso->stack_size]; + + frame = (StgClosure *)tso->sp; + + while (1) { + // If we've already marked this frame, then stop here. + if (frame->header.info == (StgInfoTable *)&stg_marked_upd_frame_info) { + goto end; + } + + info = get_ret_itbl(frame); + + switch (info->i.type) { + + case UPDATE_FRAME: + + SET_INFO(frame, (StgInfoTable *)&stg_marked_upd_frame_info); + + bh = ((StgUpdateFrame *)frame)->updatee; + + if (closure_IND(bh) || bh->header.info == &stg_BLACKHOLE_info) { + IF_DEBUG(squeeze, debugBelch("suspending duplicate work: %ld words of stack\n", (StgPtr)frame - tso->sp)); + + // If this closure is already an indirection, then + // suspend the computation up to this point: + suspendComputation(cap,tso,(StgPtr)frame); + + // Now drop the update frame, and arrange to return + // the value to the frame underneath: + tso->sp = (StgPtr)frame + sizeofW(StgUpdateFrame) - 2; + tso->sp[1] = (StgWord)bh; + tso->sp[0] = (W_)&stg_enter_info; + + // And continue with threadPaused; there might be + // yet more computation to suspend. + threadPaused(cap,tso); + return; + } + + if (bh->header.info != &stg_CAF_BLACKHOLE_info) { +#if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG) + debugBelch("Unexpected lazy BHing required at 0x%04lx\n",(long)bh); +#endif + // zero out the slop so that the sanity checker can tell + // where the next closure is. + DEBUG_FILL_SLOP(bh); +#ifdef PROFILING + // @LDV profiling + // We pretend that bh is now dead. + LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh); +#endif + SET_INFO(bh,&stg_BLACKHOLE_info); + + // We pretend that bh has just been created. + LDV_RECORD_CREATE(bh); + } + + frame = (StgClosure *) ((StgUpdateFrame *)frame + 1); + if (prev_was_update_frame) { + words_to_squeeze += sizeofW(StgUpdateFrame); + weight += weight_pending; + weight_pending = 0; + } + prev_was_update_frame = rtsTrue; + break; + + case STOP_FRAME: + goto end; + + // normal stack frames; do nothing except advance the pointer + default: + { + nat frame_size = stack_frame_sizeW(frame); + weight_pending += frame_size; + frame = (StgClosure *)((StgPtr)frame + frame_size); + prev_was_update_frame = rtsFalse; + } + } + } + +end: + IF_DEBUG(squeeze, + debugBelch("words_to_squeeze: %d, weight: %d, squeeze: %s\n", + words_to_squeeze, weight, + weight < words_to_squeeze ? "YES" : "NO")); + + // Should we squeeze or not? Arbitrary heuristic: we squeeze if + // the number of words we have to shift down is less than the + // number of stack words we squeeze away by doing so. + if (RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue && + weight < words_to_squeeze) { + stackSqueeze(tso, (StgPtr)frame); + } +} + +/* ----------------------------------------------------------------------------- + * Debugging + * -------------------------------------------------------------------------- */ + +#if DEBUG +void +printMutableList(generation *gen) +{ + bdescr *bd; + StgPtr p; + + debugBelch("@@ Mutable list %p: ", gen->mut_list); + + for (bd = gen->mut_list; bd != NULL; bd = bd->link) { + for (p = bd->start; p < bd->free; p++) { + debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p)); + } + } + debugBelch("\n"); +} +#endif /* DEBUG */ |