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#define JEMALLOC_CHUNK_DSS_C_
#include "jemalloc/internal/jemalloc_internal.h"
/******************************************************************************/
/* Data. */
const char *dss_prec_names[] = {
"disabled",
"primary",
"secondary",
"N/A"
};
/*
* Current dss precedence default, used when creating new arenas. NB: This is
* stored as unsigned rather than dss_prec_t because in principle there's no
* guarantee that sizeof(dss_prec_t) is the same as sizeof(unsigned), and we use
* atomic operations to synchronize the setting.
*/
static unsigned dss_prec_default = (unsigned)DSS_PREC_DEFAULT;
/* Base address of the DSS. */
static void *dss_base;
/* Atomic boolean indicating whether the DSS is exhausted. */
static unsigned dss_exhausted;
/* Atomic current upper limit on DSS addresses. */
static void *dss_max;
/******************************************************************************/
static void *
chunk_dss_sbrk(intptr_t increment)
{
#ifdef JEMALLOC_DSS
return (sbrk(increment));
#else
not_implemented();
return (NULL);
#endif
}
dss_prec_t
chunk_dss_prec_get(void)
{
dss_prec_t ret;
if (!have_dss)
return (dss_prec_disabled);
ret = (dss_prec_t)atomic_read_u(&dss_prec_default);
return (ret);
}
bool
chunk_dss_prec_set(dss_prec_t dss_prec)
{
if (!have_dss)
return (dss_prec != dss_prec_disabled);
atomic_write_u(&dss_prec_default, (unsigned)dss_prec);
return (false);
}
static void *
chunk_dss_max_update(void *new_addr)
{
void *max_cur;
spin_t spinner;
/*
* Get the current end of the DSS as max_cur and assure that dss_max is
* up to date.
*/
spin_init(&spinner);
while (true) {
void *max_prev = atomic_read_p(&dss_max);
max_cur = chunk_dss_sbrk(0);
if ((uintptr_t)max_prev > (uintptr_t)max_cur) {
/*
* Another thread optimistically updated dss_max. Wait
* for it to finish.
*/
spin_adaptive(&spinner);
continue;
}
if (!atomic_cas_p(&dss_max, max_prev, max_cur))
break;
}
/* Fixed new_addr can only be supported if it is at the edge of DSS. */
if (new_addr != NULL && max_cur != new_addr)
return (NULL);
return (max_cur);
}
void *
chunk_alloc_dss(tsdn_t *tsdn, arena_t *arena, void *new_addr, size_t size,
size_t alignment, bool *zero, bool *commit)
{
cassert(have_dss);
assert(size > 0 && (size & chunksize_mask) == 0);
assert(alignment > 0 && (alignment & chunksize_mask) == 0);
/*
* sbrk() uses a signed increment argument, so take care not to
* interpret a huge allocation request as a negative increment.
*/
if ((intptr_t)size < 0)
return (NULL);
if (!atomic_read_u(&dss_exhausted)) {
/*
* The loop is necessary to recover from races with other
* threads that are using the DSS for something other than
* malloc.
*/
while (true) {
void *ret, *cpad, *max_cur, *dss_next, *dss_prev;
size_t gap_size, cpad_size;
intptr_t incr;
max_cur = chunk_dss_max_update(new_addr);
if (max_cur == NULL)
goto label_oom;
/*
* Calculate how much padding is necessary to
* chunk-align the end of the DSS.
*/
gap_size = (chunksize - CHUNK_ADDR2OFFSET(dss_max)) &
chunksize_mask;
/*
* Compute how much chunk-aligned pad space (if any) is
* necessary to satisfy alignment. This space can be
* recycled for later use.
*/
cpad = (void *)((uintptr_t)dss_max + gap_size);
ret = (void *)ALIGNMENT_CEILING((uintptr_t)dss_max,
alignment);
cpad_size = (uintptr_t)ret - (uintptr_t)cpad;
dss_next = (void *)((uintptr_t)ret + size);
if ((uintptr_t)ret < (uintptr_t)dss_max ||
(uintptr_t)dss_next < (uintptr_t)dss_max)
goto label_oom; /* Wrap-around. */
incr = gap_size + cpad_size + size;
/*
* Optimistically update dss_max, and roll back below if
* sbrk() fails. No other thread will try to extend the
* DSS while dss_max is greater than the current DSS
* max reported by sbrk(0).
*/
if (atomic_cas_p(&dss_max, max_cur, dss_next))
continue;
/* Try to allocate. */
dss_prev = chunk_dss_sbrk(incr);
if (dss_prev == max_cur) {
/* Success. */
if (cpad_size != 0) {
chunk_hooks_t chunk_hooks =
CHUNK_HOOKS_INITIALIZER;
chunk_dalloc_wrapper(tsdn, arena,
&chunk_hooks, cpad, cpad_size,
arena_extent_sn_next(arena), false,
true);
}
if (*zero) {
JEMALLOC_VALGRIND_MAKE_MEM_UNDEFINED(
ret, size);
memset(ret, 0, size);
}
if (!*commit)
*commit = pages_decommit(ret, size);
return (ret);
}
/*
* Failure, whether due to OOM or a race with a raw
* sbrk() call from outside the allocator. Try to roll
* back optimistic dss_max update; if rollback fails,
* it's due to another caller of this function having
* succeeded since this invocation started, in which
* case rollback is not necessary.
*/
atomic_cas_p(&dss_max, dss_next, max_cur);
if (dss_prev == (void *)-1) {
/* OOM. */
atomic_write_u(&dss_exhausted, (unsigned)true);
goto label_oom;
}
}
}
label_oom:
return (NULL);
}
static bool
chunk_in_dss_helper(void *chunk, void *max)
{
return ((uintptr_t)chunk >= (uintptr_t)dss_base && (uintptr_t)chunk <
(uintptr_t)max);
}
bool
chunk_in_dss(void *chunk)
{
cassert(have_dss);
return (chunk_in_dss_helper(chunk, atomic_read_p(&dss_max)));
}
bool
chunk_dss_mergeable(void *chunk_a, void *chunk_b)
{
void *max;
cassert(have_dss);
max = atomic_read_p(&dss_max);
return (chunk_in_dss_helper(chunk_a, max) ==
chunk_in_dss_helper(chunk_b, max));
}
void
chunk_dss_boot(void)
{
cassert(have_dss);
dss_base = chunk_dss_sbrk(0);
dss_exhausted = (unsigned)(dss_base == (void *)-1);
dss_max = dss_base;
}
/******************************************************************************/
|
