diff options
Diffstat (limited to 'erts/emulator/beam/erl_db_hash.c')
| -rw-r--r-- | erts/emulator/beam/erl_db_hash.c | 250 |
1 files changed, 181 insertions, 69 deletions
diff --git a/erts/emulator/beam/erl_db_hash.c b/erts/emulator/beam/erl_db_hash.c index 5937bd64ec..2bcdb47a54 100644 --- a/erts/emulator/beam/erl_db_hash.c +++ b/erts/emulator/beam/erl_db_hash.c @@ -93,11 +93,9 @@ erts_flxctr_dec_read_centralized(&(DB)->common.counters, ERTS_DB_TABLE_NITEMS_COUNTER_ID) #define RESET_NITEMS(DB) \ erts_flxctr_reset(&(DB)->common.counters, ERTS_DB_TABLE_NITEMS_COUNTER_ID) -/* - * The following symbols can be manipulated to "tune" the linear hash array - */ + #define GROW_LIMIT(NACTIVE) ((NACTIVE)*1) -#define SHRINK_LIMIT(NACTIVE) ((NACTIVE) / 2) +#define SHRINK_LIMIT(TB) erts_atomic_read_nob(&(TB)->shrink_limit) /* ** We want the first mandatory segment to be small (to reduce minimal footprint) @@ -137,6 +135,11 @@ #define BUCKET(tb, i) SEGTAB(tb)[SLOT_IX_TO_SEG_IX(i)]->buckets[(i) & EXT_SEGSZ_MASK] +#ifdef DEBUG +# define DBG_BUCKET_INACTIVE ((HashDbTerm*)0xdead5107) +#endif + + /* * When deleting a table, the number of records to delete. * Approximate number, because we must delete entire buckets. @@ -377,7 +380,7 @@ typedef int (*extra_match_validator_t)(int keypos, Eterm match, Eterm guard, Ete */ static struct ext_segtab* alloc_ext_segtab(DbTableHash* tb, unsigned seg_ix); static void alloc_seg(DbTableHash *tb); -static int free_seg(DbTableHash *tb, int free_records); +static int free_seg(DbTableHash *tb); static HashDbTerm* next_live(DbTableHash *tb, Uint *iptr, erts_rwmtx_t** lck_ptr, HashDbTerm *list); static HashDbTerm* search_list(DbTableHash* tb, Eterm key, @@ -476,10 +479,8 @@ static int db_raw_next_hash(Process* p, DbTable *tbl, Eterm key, Eterm *ret); static ERTS_INLINE void try_shrink(DbTableHash* tb) { - int nactive = NACTIVE(tb); int nitems = NITEMS(tb); - if (nactive > FIRST_SEGSZ && nitems < SHRINK_LIMIT(nactive) - && !IS_FIXED(tb)) { + if (nitems < SHRINK_LIMIT(tb) && !IS_FIXED(tb)) { shrink(tb, nitems); } } @@ -693,6 +694,7 @@ int db_create_hash(Process *p, DbTable *tbl) erts_atomic_init_nob(&tb->szm, FIRST_SEGSZ_MASK); erts_atomic_init_nob(&tb->nactive, FIRST_SEGSZ); + erts_atomic_init_nob(&tb->shrink_limit, 0); erts_atomic_init_nob(&tb->fixdel, (erts_aint_t)NULL); erts_atomic_init_nob(&tb->segtab, (erts_aint_t)NULL); SET_SEGTAB(tb, tb->first_segtab); @@ -779,7 +781,7 @@ static int db_next_hash(Process *p, DbTable *tbl, Eterm key, Eterm *ret) b = next_live(tb, &ix, &lck, b->next); if (tb->common.status & (DB_BAG | DB_DUPLICATE_BAG)) { while (b != 0) { - if (!has_key(tb, b, key, hval) && !is_pseudo_deleted(b)) { + if (!has_key(tb, b, key, hval)) { break; } b = next_live(tb, &ix, &lck, b->next); @@ -789,6 +791,7 @@ static int db_next_hash(Process *p, DbTable *tbl, Eterm key, Eterm *ret) *ret = am_EOT; } else { + ASSERT(!is_pseudo_deleted(b)); *ret = db_copy_key(p, tbl, &b->dbterm); RUNLOCK_HASH(lck); } @@ -2474,7 +2477,7 @@ static SWord db_free_table_continue_hash(DbTable *tbl, SWord reds) erts_atomic_set_relb(&tb->fixdel, (erts_aint_t)NULL); while(tb->nslots != 0) { - reds -= EXT_SEGSZ/64 + free_seg(tb, 1); + reds -= EXT_SEGSZ/64 + free_seg(tb); /* * If we have done enough work, get out here. @@ -2672,6 +2675,34 @@ static struct ext_segtab* alloc_ext_segtab(DbTableHash* tb, unsigned seg_ix) return est; } +static void calc_shrink_limit(DbTableHash* tb) +{ + erts_aint_t shrink_limit; + + if (tb->nslots >= (FIRST_SEGSZ + 2*EXT_SEGSZ)) { + /* + * Start shrink when we can remove one extra segment + * and still remain below 50% load. + */ + shrink_limit = (tb->nslots - EXT_SEGSZ) / 2; + } + else { + /* + * But don't shrink below two segments. + * Why? In order to have chance of getting rid of the last extra segment, + * and rehash it into the first small segment, we either have to start + * early and do speculative joining of buckets or we have to join a lot + * of buckets during each delete-op. + * + * Instead keep segment #2 once allocated. I also think it's a good bet + * a shrinking large table will grow large again. + */ + shrink_limit = 0; + } + erts_atomic_set_nob(&tb->shrink_limit, shrink_limit); +} + + /* Extend table with one new segment */ static void alloc_seg(DbTableHash *tb) @@ -2690,8 +2721,17 @@ static void alloc_seg(DbTableHash *tb) segtab[seg_ix] = (struct segment*) erts_db_alloc(ERTS_ALC_T_DB_SEG, (DbTable *) tb, SIZEOF_SEGMENT(EXT_SEGSZ)); - sys_memset(segtab[seg_ix], 0, SIZEOF_SEGMENT(EXT_SEGSZ)); +#ifdef DEBUG + { + int i; + for (i = 0; i < EXT_SEGSZ; i++) { + segtab[seg_ix]->buckets[i] = DBG_BUCKET_INACTIVE; + } + } +#endif tb->nslots += EXT_SEGSZ; + + calc_shrink_limit(tb); } static void dealloc_ext_segtab(void* lop_data) @@ -2701,10 +2741,19 @@ static void dealloc_ext_segtab(void* lop_data) erts_free(ERTS_ALC_T_DB_SEG, est); } -/* Shrink table by freeing the top segment +struct dealloc_seg_ops { + struct segment* segp; + Uint seg_sz; + + struct ext_segtab* est; +}; + +/* Shrink table by removing the top segment ** free_records: 1=free any records in segment, 0=assume segment is empty +** ds_ops: (out) Instructions for dealloc_seg(). */ -static int free_seg(DbTableHash *tb, int free_records) +static int remove_seg(DbTableHash *tb, int free_records, + struct dealloc_seg_ops *ds_ops) { const int seg_ix = SLOT_IX_TO_SEG_IX(tb->nslots) - 1; struct segment** const segtab = SEGTAB(tb); @@ -2712,24 +2761,47 @@ static int free_seg(DbTableHash *tb, int free_records) Uint seg_sz; int nrecords = 0; + ERTS_LC_ASSERT(IS_TAB_WLOCKED(tb) || tb->common.status & DB_DELETE + || erts_atomic_read_nob(&tb->is_resizing)); + ASSERT(segp != NULL); -#ifndef DEBUG - if (free_records) -#endif - { - int i = (seg_ix == 0) ? FIRST_SEGSZ : EXT_SEGSZ; - while (i--) { - HashDbTerm* p = segp->buckets[i]; + if (free_records) { + int ix, n; + if (seg_ix == 0) { + /* First segment (always fully active) */ + n = FIRST_SEGSZ; + ix = FIRST_SEGSZ-1; + } + else if (NACTIVE(tb) < tb->nslots) { + /* Last extended segment partially active */ + n = (NACTIVE(tb) - FIRST_SEGSZ) & EXT_SEGSZ_MASK; + ix = (NACTIVE(tb)-1) & EXT_SEGSZ_MASK; + } + else { + /* Full extended segment */ + n = EXT_SEGSZ; + ix = EXT_SEGSZ - 1; + } + for ( ; n > 0; n--, ix--) { + HashDbTerm* p = segp->buckets[ix & EXT_SEGSZ_MASK]; while(p != 0) { HashDbTerm* nxt = p->next; - ASSERT(free_records); /* segment not empty as assumed? */ free_term(tb, p); p = nxt; ++nrecords; } } } - +#ifdef DEBUG + else { + int ix = (seg_ix == 0) ? FIRST_SEGSZ-1 : EXT_SEGSZ-1; + for ( ; ix >= 0; ix--) { + ASSERT(segp->buckets[ix] == DBG_BUCKET_INACTIVE); + } + } +#endif + + ds_ops->est = NULL; if (seg_ix >= NSEG_1) { struct ext_segtab* est = ErtsContainerStruct_(segtab,struct ext_segtab,segtab); @@ -2738,35 +2810,64 @@ static int free_seg(DbTableHash *tb, int free_records) SET_SEGTAB(tb, est->prev_segtab); tb->nsegs = est->prev_nsegs; - if (!tb->common.is_thread_safe) { - /* - * Table is doing a graceful shrink operation and we must avoid - * deallocating this segtab while it may still be read by other - * threads. Schedule deallocation with thread progress to make - * sure no lingering threads are still hanging in BUCKET macro - * with an old segtab pointer. - */ - erts_schedule_db_free(&tb->common, dealloc_ext_segtab, - est, &est->lop, - SIZEOF_EXT_SEGTAB(est->nsegs)); - } - else - erts_db_free(ERTS_ALC_T_DB_SEG, (DbTable*)tb, est, - SIZEOF_EXT_SEGTAB(est->nsegs)); + ds_ops->est = est; } } + seg_sz = (seg_ix == 0) ? FIRST_SEGSZ : EXT_SEGSZ; - erts_db_free(ERTS_ALC_T_DB_SEG, (DbTable *)tb, segp, SIZEOF_SEGMENT(seg_sz)); + tb->nslots -= seg_sz; + ASSERT(tb->nslots >= 0); + + ds_ops->segp = segp; + ds_ops->seg_sz = seg_sz; #ifdef DEBUG if (seg_ix < tb->nsegs) SEGTAB(tb)[seg_ix] = NULL; #endif - tb->nslots -= seg_sz; - ASSERT(tb->nslots >= 0); + calc_shrink_limit(tb); return nrecords; } +/* + * Deallocate segment removed by remove_seg() + */ +static void dealloc_seg(DbTableHash *tb, struct dealloc_seg_ops* ds_ops) +{ + struct ext_segtab* est = ds_ops->est; + + if (est) { + if (!tb->common.is_thread_safe) { + /* + * Table is doing a graceful shrink operation and we must avoid + * deallocating this segtab while it may still be read by other + * threads. Schedule deallocation with thread progress to make + * sure no lingering threads are still hanging in BUCKET macro + * with an old segtab pointer. + */ + erts_schedule_db_free(&tb->common, dealloc_ext_segtab, + est, &est->lop, + SIZEOF_EXT_SEGTAB(est->nsegs)); + } + else + erts_db_free(ERTS_ALC_T_DB_SEG, (DbTable*)tb, est, + SIZEOF_EXT_SEGTAB(est->nsegs)); + } + + erts_db_free(ERTS_ALC_T_DB_SEG, (DbTable *)tb, + ds_ops->segp, SIZEOF_SEGMENT(ds_ops->seg_sz)); +} + +/* Remove and deallocate top segment and all its contained objects */ +static int free_seg(DbTableHash *tb) +{ + struct dealloc_seg_ops ds_ops; + int reds; + + reds = remove_seg(tb, 1, &ds_ops); + dealloc_seg(tb, &ds_ops); + return reds; +} /* ** Copy terms from ptr1 until ptr2 @@ -2888,6 +2989,7 @@ static void grow(DbTableHash* tb, int nitems) pnext = &BUCKET(tb, from_ix); p = *pnext; to_pnext = &BUCKET(tb, to_ix); + ASSERT(*to_pnext == DBG_BUCKET_INACTIVE); while (p != NULL) { if (is_pseudo_deleted(p)) { /* rare but possible with fine locking */ *pnext = p->next; @@ -2924,19 +3026,21 @@ abort: */ static void shrink(DbTableHash* tb, int nitems) { - HashDbTerm** src_bp; - HashDbTerm** dst_bp; + struct dealloc_seg_ops ds_ops; + HashDbTerm* src; + HashDbTerm* tail; HashDbTerm** bp; erts_rwmtx_t* lck; int src_ix, dst_ix, low_szm; int nactive; int loop_limit = 5; + ds_ops.segp = NULL; do { if (!begin_resizing(tb)) return; /* already in progress */ nactive = NACTIVE(tb); - if (!(nactive > FIRST_SEGSZ && nitems < SHRINK_LIMIT(nactive))) { + if (!(nitems < SHRINK_LIMIT(tb))) { goto abort; /* already done (race) */ } src_ix = nactive - 1; @@ -2953,41 +3057,49 @@ static void shrink(DbTableHash* tb, int nitems) goto abort; } - src_bp = &BUCKET(tb, src_ix); - dst_bp = &BUCKET(tb, dst_ix); - bp = src_bp; - - /* - * We join lists by appending "dst" at the end of "src" - * as we must step through "src" anyway to purge pseudo deleted. - */ - while(*bp != NULL) { - if (is_pseudo_deleted(*bp)) { - HashDbTerm* deleted = *bp; - *bp = deleted->next; - free_term(tb, deleted); - } else { - bp = &(*bp)->next; - } - } - *bp = *dst_bp; - *dst_bp = *src_bp; - *src_bp = NULL; - + src = BUCKET(tb, src_ix); +#ifdef DEBUG + BUCKET(tb, src_ix) = DBG_BUCKET_INACTIVE; +#endif nactive = src_ix; erts_atomic_set_nob(&tb->nactive, nactive); if (dst_ix == 0) { erts_atomic_set_relb(&tb->szm, low_szm); } - WUNLOCK_HASH(lck); - if (tb->nslots - src_ix >= EXT_SEGSZ) { - free_seg(tb, 0); + remove_seg(tb, 0, &ds_ops); } done_resizing(tb); - } while (--loop_limit - && nactive > FIRST_SEGSZ && nitems < SHRINK_LIMIT(nactive)); + if (src) { + /* + * We join buckets by appending "dst" list at the end of "src" list + * as we must step through "src" anyway to purge pseudo deleted. + */ + bp = &BUCKET(tb, dst_ix); + tail = *bp; + *bp = src; + + while(*bp != NULL) { + if (is_pseudo_deleted(*bp)) { + HashDbTerm* deleted = *bp; + *bp = deleted->next; + free_term(tb, deleted); + } else { + bp = &(*bp)->next; + } + } + *bp = tail; + } + + WUNLOCK_HASH(lck); + + if (ds_ops.segp) { + dealloc_seg(tb, &ds_ops); + ds_ops.segp = NULL; + } + + } while (--loop_limit && nitems < SHRINK_LIMIT(tb)); return; abort: |