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Fast-path improvement: reduce # of branches and unnecessary operations.

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- Combine multiple runtime branches into a single malloc_slow check.
- Avoid calling arena_choose / size2index / index2size on fast path.
- A few micro optimizations.
This commit is contained in:
Qi Wang
2015-10-27 15:12:10 -07:00
committed by Jason Evans
parent 710ca112e3
commit f4a0f32d34
11 changed files with 357 additions and 214 deletions
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116
include/jemalloc/internal/tcache.h
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@@ -70,6 +70,13 @@ struct tcache_bin_s {
int low_water; /* Min # cached since last GC. */
unsigned lg_fill_div; /* Fill (ncached_max >> lg_fill_div). */
unsigned ncached; /* # of cached objects. */
/*
* To make use of adjacent cacheline prefetch, the items in the avail
* stack goes to higher address for newer allocations. avail points
* just above the available space, which means that
* avail[-ncached, ... 1] are available items and the lowest item will
* be allocated first.
*/
void **avail; /* Stack of available objects. */
};
@@ -126,7 +133,7 @@ extern tcaches_t *tcaches;
size_t tcache_salloc(const void *ptr);
void tcache_event_hard(tsd_t *tsd, tcache_t *tcache);
void *tcache_alloc_small_hard(tsd_t *tsd, arena_t *arena, tcache_t *tcache,
tcache_bin_t *tbin, szind_t binind);
tcache_bin_t *tbin, szind_t binind, bool *tcache_success);
void tcache_bin_flush_small(tsd_t *tsd, tcache_t *tcache, tcache_bin_t *tbin,
szind_t binind, unsigned rem);
void tcache_bin_flush_large(tsd_t *tsd, tcache_bin_t *tbin, szind_t binind,
@@ -155,15 +162,15 @@ void tcache_flush(void);
bool tcache_enabled_get(void);
tcache_t *tcache_get(tsd_t *tsd, bool create);
void tcache_enabled_set(bool enabled);
void *tcache_alloc_easy(tcache_bin_t *tbin);
void *tcache_alloc_easy(tcache_bin_t *tbin, bool *tcache_success);
void *tcache_alloc_small(tsd_t *tsd, arena_t *arena, tcache_t *tcache,
size_t size, bool zero);
size_t size, szind_t ind, bool zero, bool slow_path);
void *tcache_alloc_large(tsd_t *tsd, arena_t *arena, tcache_t *tcache,
size_t size, bool zero);
size_t size, szind_t ind, bool zero, bool slow_path);
void tcache_dalloc_small(tsd_t *tsd, tcache_t *tcache, void *ptr,
szind_t binind);
szind_t binind, bool slow_path);
void tcache_dalloc_large(tsd_t *tsd, tcache_t *tcache, void *ptr,
size_t size);
size_t size, bool slow_path);
tcache_t *tcaches_get(tsd_t *tsd, unsigned ind);
#endif
@@ -247,44 +254,69 @@ tcache_event(tsd_t *tsd, tcache_t *tcache)
}
JEMALLOC_ALWAYS_INLINE void *
tcache_alloc_easy(tcache_bin_t *tbin)
tcache_alloc_easy(tcache_bin_t *tbin, bool *tcache_success)
{
void *ret;
if (unlikely(tbin->ncached == 0)) {
tbin->low_water = -1;
*tcache_success = false;
return (NULL);
}
/*
* tcache_success (instead of ret) should be checked upon the return of
* this function. We avoid checking (ret == NULL) because there is
* never a null stored on the avail stack (which is unknown to the
* compiler), and eagerly checking ret would cause pipeline stall
* (waiting for the cacheline).
*/
*tcache_success = true;
ret = *(tbin->avail - tbin->ncached);
tbin->ncached--;
if (unlikely((int)tbin->ncached < tbin->low_water))
tbin->low_water = tbin->ncached;
ret = tbin->avail[tbin->ncached];
return (ret);
}
JEMALLOC_ALWAYS_INLINE void *
tcache_alloc_small(tsd_t *tsd, arena_t *arena, tcache_t *tcache, size_t size,
bool zero)
szind_t binind, bool zero, bool slow_path)
{
void *ret;
szind_t binind;
size_t usize;
tcache_bin_t *tbin;
bool tcache_success;
size_t usize JEMALLOC_CC_SILENCE_INIT(0);
binind = size2index(size);
assert(binind < NBINS);
tbin = &tcache->tbins[binind];
usize = index2size(binind);
ret = tcache_alloc_easy(tbin);
if (unlikely(ret == NULL)) {
ret = tcache_alloc_small_hard(tsd, arena, tcache, tbin, binind);
if (ret == NULL)
ret = tcache_alloc_easy(tbin, &tcache_success);
assert(tcache_success == (ret != NULL));
if (unlikely(!tcache_success)) {
bool tcache_hard_success;
arena = arena_choose(tsd, arena);
if (unlikely(arena == NULL))
return (NULL);
ret = tcache_alloc_small_hard(tsd, arena, tcache, tbin, binind,
&tcache_hard_success);
if (tcache_hard_success == false)
return (NULL);
}
assert(tcache_salloc(ret) == usize);
assert(ret);
/*
* Only compute usize if required. The checks in the following if
* statement are all static.
*/
if (config_prof || (slow_path && config_fill) || unlikely(zero)) {
usize = index2size(binind);
assert(tcache_salloc(ret) == usize);
}
if (likely(!zero)) {
if (config_fill) {
if (slow_path && config_fill) {
if (unlikely(opt_junk_alloc)) {
arena_alloc_junk_small(ret,
&arena_bin_info[binind], false);
@@ -292,7 +324,7 @@ tcache_alloc_small(tsd_t *tsd, arena_t *arena, tcache_t *tcache, size_t size,
memset(ret, 0, usize);
}
} else {
if (config_fill && unlikely(opt_junk_alloc)) {
if (slow_path && config_fill && unlikely(opt_junk_alloc)) {
arena_alloc_junk_small(ret, &arena_bin_info[binind],
true);
}
@@ -309,28 +341,38 @@ tcache_alloc_small(tsd_t *tsd, arena_t *arena, tcache_t *tcache, size_t size,
JEMALLOC_ALWAYS_INLINE void *
tcache_alloc_large(tsd_t *tsd, arena_t *arena, tcache_t *tcache, size_t size,
bool zero)
szind_t binind, bool zero, bool slow_path)
{
void *ret;
szind_t binind;
size_t usize;
tcache_bin_t *tbin;
bool tcache_success;
size_t usize JEMALLOC_CC_SILENCE_INIT(0);
binind = size2index(size);
usize = index2size(binind);
assert(usize <= tcache_maxclass);
assert(binind < nhbins);
tbin = &tcache->tbins[binind];
ret = tcache_alloc_easy(tbin);
if (unlikely(ret == NULL)) {
ret = tcache_alloc_easy(tbin, &tcache_success);
assert(tcache_success == (ret != NULL));
if (unlikely(!tcache_success)) {
/*
* Only allocate one large object at a time, because it's quite
* expensive to create one and not use it.
*/
ret = arena_malloc_large(arena, usize, zero);
arena = arena_choose(tsd, arena);
if (unlikely(arena == NULL))
return (NULL);
usize = index2size(binind);
assert(usize <= tcache_maxclass);
ret = arena_malloc_large(arena, usize, binind, zero);
if (ret == NULL)
return (NULL);
} else {
/* Only compute usize on demand */
if (config_prof || (slow_path && config_fill) || unlikely(zero)) {
usize = index2size(binind);
assert(usize <= tcache_maxclass);
}
if (config_prof && usize == LARGE_MINCLASS) {
arena_chunk_t *chunk =
(arena_chunk_t *)CHUNK_ADDR2BASE(ret);
@@ -340,7 +382,7 @@ tcache_alloc_large(tsd_t *tsd, arena_t *arena, tcache_t *tcache, size_t size,
BININD_INVALID);
}
if (likely(!zero)) {
if (config_fill) {
if (slow_path && config_fill) {
if (unlikely(opt_junk_alloc))
memset(ret, 0xa5, usize);
else if (unlikely(opt_zero))
@@ -360,14 +402,15 @@ tcache_alloc_large(tsd_t *tsd, arena_t *arena, tcache_t *tcache, size_t size,
}
JEMALLOC_ALWAYS_INLINE void
tcache_dalloc_small(tsd_t *tsd, tcache_t *tcache, void *ptr, szind_t binind)
tcache_dalloc_small(tsd_t *tsd, tcache_t *tcache, void *ptr, szind_t binind,
bool slow_path)
{
tcache_bin_t *tbin;
tcache_bin_info_t *tbin_info;
assert(tcache_salloc(ptr) <= SMALL_MAXCLASS);
if (config_fill && unlikely(opt_junk_free))
if (slow_path && config_fill && unlikely(opt_junk_free))
arena_dalloc_junk_small(ptr, &arena_bin_info[binind]);
tbin = &tcache->tbins[binind];
@@ -377,14 +420,15 @@ tcache_dalloc_small(tsd_t *tsd, tcache_t *tcache, void *ptr, szind_t binind)
(tbin_info->ncached_max >> 1));
}
assert(tbin->ncached < tbin_info->ncached_max);
tbin->avail[tbin->ncached] = ptr;
tbin->ncached++;
*(tbin->avail - tbin->ncached) = ptr;
tcache_event(tsd, tcache);
}
JEMALLOC_ALWAYS_INLINE void
tcache_dalloc_large(tsd_t *tsd, tcache_t *tcache, void *ptr, size_t size)
tcache_dalloc_large(tsd_t *tsd, tcache_t *tcache, void *ptr, size_t size,
bool slow_path)
{
szind_t binind;
tcache_bin_t *tbin;
@@ -396,7 +440,7 @@ tcache_dalloc_large(tsd_t *tsd, tcache_t *tcache, void *ptr, size_t size)
binind = size2index(size);
if (config_fill && unlikely(opt_junk_free))
if (slow_path && config_fill && unlikely(opt_junk_free))
arena_dalloc_junk_large(ptr, size);
tbin = &tcache->tbins[binind];
@@ -406,8 +450,8 @@ tcache_dalloc_large(tsd_t *tsd, tcache_t *tcache, void *ptr, size_t size)
(tbin_info->ncached_max >> 1), tcache);
}
assert(tbin->ncached < tbin_info->ncached_max);
tbin->avail[tbin->ncached] = ptr;
tbin->ncached++;
*(tbin->avail - tbin->ncached) = ptr;
tcache_event(tsd, tcache);
}