server-skynet-source-3rd-je.../src/huge.c
Daniel Micay a95018ee81 Attempt to expand huge allocations in-place.
This adds support for expanding huge allocations in-place by requesting
memory at a specific address from the chunk allocator.

It's currently only implemented for the chunk recycling path, although
in theory it could also be done by optimistically allocating new chunks.
On Linux, it could attempt an in-place mremap. However, that won't work
in practice since the heap is grown downwards and memory is not unmapped
(in a normal build, at least).

Repeated vector reallocation micro-benchmark:

    #include <string.h>
    #include <stdlib.h>

    int main(void) {
        for (size_t i = 0; i < 100; i++) {
            void *ptr = NULL;
            size_t old_size = 0;
            for (size_t size = 4; size < (1 << 30); size *= 2) {
                ptr = realloc(ptr, size);
                if (!ptr) return 1;
                memset(ptr + old_size, 0xff, size - old_size);
                old_size = size;
            }
            free(ptr);
        }
    }

The glibc allocator fails to do any in-place reallocations on this
benchmark once it passes the M_MMAP_THRESHOLD (default 128k) but it
elides the cost of copies via mremap, which is currently not something
that jemalloc can use.

With this improvement, jemalloc still fails to do any in-place huge
reallocations for the first outer loop, but then succeeds 100% of the
time for the remaining 99 iterations. The time spent doing allocations
and copies drops down to under 5%, with nearly all of it spent doing
purging + faulting (when huge pages are disabled) and the array memset.

An improved mremap API (MREMAP_RETAIN - #138) would be far more general
but this is a portable optimization and would still be useful on Linux
for xallocx.

Numbers with transparent huge pages enabled:

glibc (copies elided via MREMAP_MAYMOVE): 8.471s

jemalloc: 17.816s
jemalloc + no-op madvise: 13.236s

jemalloc + this commit: 6.787s
jemalloc + this commit + no-op madvise: 6.144s

Numbers with transparent huge pages disabled:

glibc (copies elided via MREMAP_MAYMOVE): 15.403s

jemalloc: 39.456s
jemalloc + no-op madvise: 12.768s

jemalloc + this commit: 15.534s
jemalloc + this commit + no-op madvise: 6.354s

Closes #137
2014-10-05 14:47:01 -07:00

371 lines
8.0 KiB
C

#define JEMALLOC_HUGE_C_
#include "jemalloc/internal/jemalloc_internal.h"
/******************************************************************************/
/* Data. */
/* Protects chunk-related data structures. */
static malloc_mutex_t huge_mtx;
/******************************************************************************/
/* Tree of chunks that are stand-alone huge allocations. */
static extent_tree_t huge;
void *
huge_malloc(tsd_t *tsd, arena_t *arena, size_t size, bool zero)
{
return (huge_palloc(tsd, arena, size, chunksize, zero));
}
void *
huge_palloc(tsd_t *tsd, arena_t *arena, size_t size, size_t alignment,
bool zero)
{
void *ret;
size_t csize;
extent_node_t *node;
bool is_zeroed;
/* Allocate one or more contiguous chunks for this request. */
csize = CHUNK_CEILING(size);
if (csize == 0) {
/* size is large enough to cause size_t wrap-around. */
return (NULL);
}
/* Allocate an extent node with which to track the chunk. */
node = base_node_alloc();
if (node == NULL)
return (NULL);
/*
* Copy zero into is_zeroed and pass the copy to chunk_alloc(), so that
* it is possible to make correct junk/zero fill decisions below.
*/
is_zeroed = zero;
arena = choose_arena(tsd, arena);
ret = arena_chunk_alloc_huge(arena, NULL, csize, alignment, &is_zeroed);
if (ret == NULL) {
base_node_dalloc(node);
return (NULL);
}
/* Insert node into huge. */
node->addr = ret;
node->size = csize;
node->arena = arena;
malloc_mutex_lock(&huge_mtx);
extent_tree_ad_insert(&huge, node);
malloc_mutex_unlock(&huge_mtx);
if (config_fill && !zero) {
if (unlikely(opt_junk))
memset(ret, 0xa5, csize);
else if (unlikely(opt_zero) && !is_zeroed)
memset(ret, 0, csize);
}
return (ret);
}
#ifdef JEMALLOC_JET
#undef huge_dalloc_junk
#define huge_dalloc_junk JEMALLOC_N(huge_dalloc_junk_impl)
#endif
static void
huge_dalloc_junk(void *ptr, size_t usize)
{
if (config_fill && have_dss && unlikely(opt_junk)) {
/*
* Only bother junk filling if the chunk isn't about to be
* unmapped.
*/
if (!config_munmap || (have_dss && chunk_in_dss(ptr)))
memset(ptr, 0x5a, usize);
}
}
#ifdef JEMALLOC_JET
#undef huge_dalloc_junk
#define huge_dalloc_junk JEMALLOC_N(huge_dalloc_junk)
huge_dalloc_junk_t *huge_dalloc_junk = JEMALLOC_N(huge_dalloc_junk_impl);
#endif
static bool
huge_ralloc_no_move_expand(void *ptr, size_t oldsize, size_t size, bool zero) {
size_t csize;
void *expand_addr;
size_t expand_size;
extent_node_t *node, key;
arena_t *arena;
bool is_zeroed;
void *ret;
csize = CHUNK_CEILING(size);
if (csize == 0) {
/* size is large enough to cause size_t wrap-around. */
return (true);
}
expand_addr = ptr + oldsize;
expand_size = csize - oldsize;
malloc_mutex_lock(&huge_mtx);
key.addr = ptr;
node = extent_tree_ad_search(&huge, &key);
assert(node != NULL);
assert(node->addr == ptr);
/* Find the current arena. */
arena = node->arena;
malloc_mutex_unlock(&huge_mtx);
/*
* Copy zero into is_zeroed and pass the copy to chunk_alloc(), so that
* it is possible to make correct junk/zero fill decisions below.
*/
is_zeroed = zero;
ret = arena_chunk_alloc_huge(arena, expand_addr, expand_size, chunksize,
&is_zeroed);
if (ret == NULL)
return (true);
assert(ret == expand_addr);
malloc_mutex_lock(&huge_mtx);
/* Update the size of the huge allocation. */
node->size = csize;
malloc_mutex_unlock(&huge_mtx);
if (config_fill && !zero) {
if (unlikely(opt_junk))
memset(expand_addr, 0xa5, expand_size);
else if (unlikely(opt_zero) && !is_zeroed)
memset(expand_addr, 0, expand_size);
}
return (false);
}
bool
huge_ralloc_no_move(void *ptr, size_t oldsize, size_t size, size_t extra,
bool zero)
{
/* Both allocations must be huge to avoid a move. */
if (oldsize <= arena_maxclass)
return (true);
assert(CHUNK_CEILING(oldsize) == oldsize);
/*
* Avoid moving the allocation if the size class can be left the same.
*/
if (CHUNK_CEILING(oldsize) >= CHUNK_CEILING(size)
&& CHUNK_CEILING(oldsize) <= CHUNK_CEILING(size+extra)) {
return (false);
}
/* Overflow. */
if (CHUNK_CEILING(size) == 0)
return (true);
/* Shrink the allocation in-place. */
if (CHUNK_CEILING(oldsize) > CHUNK_CEILING(size)) {
extent_node_t *node, key;
void *excess_addr;
size_t excess_size;
malloc_mutex_lock(&huge_mtx);
key.addr = ptr;
node = extent_tree_ad_search(&huge, &key);
assert(node != NULL);
assert(node->addr == ptr);
/* Update the size of the huge allocation. */
node->size = CHUNK_CEILING(size);
malloc_mutex_unlock(&huge_mtx);
excess_addr = node->addr + CHUNK_CEILING(size);
excess_size = CHUNK_CEILING(oldsize) - CHUNK_CEILING(size);
/* Zap the excess chunks. */
huge_dalloc_junk(excess_addr, excess_size);
arena_chunk_dalloc_huge(node->arena, excess_addr, excess_size);
return (false);
}
/* Attempt to expand the allocation in-place. */
if (huge_ralloc_no_move_expand(ptr, oldsize, size + extra, zero)) {
if (extra == 0)
return (true);
/* Try again, this time without extra. */
return (huge_ralloc_no_move_expand(ptr, oldsize, size, zero));
}
return (false);
}
void *
huge_ralloc(tsd_t *tsd, arena_t *arena, void *ptr, size_t oldsize, size_t size,
size_t extra, size_t alignment, bool zero, bool try_tcache_dalloc)
{
void *ret;
size_t copysize;
/* Try to avoid moving the allocation. */
if (!huge_ralloc_no_move(ptr, oldsize, size, extra, zero))
return (ptr);
/*
* size and oldsize are different enough that we need to use a
* different size class. In that case, fall back to allocating new
* space and copying.
*/
if (alignment > chunksize)
ret = huge_palloc(tsd, arena, size + extra, alignment, zero);
else
ret = huge_malloc(tsd, arena, size + extra, zero);
if (ret == NULL) {
if (extra == 0)
return (NULL);
/* Try again, this time without extra. */
if (alignment > chunksize)
ret = huge_palloc(tsd, arena, size, alignment, zero);
else
ret = huge_malloc(tsd, arena, size, zero);
if (ret == NULL)
return (NULL);
}
/*
* Copy at most size bytes (not size+extra), since the caller has no
* expectation that the extra bytes will be reliably preserved.
*/
copysize = (size < oldsize) ? size : oldsize;
memcpy(ret, ptr, copysize);
iqalloc(tsd, ptr, try_tcache_dalloc);
return (ret);
}
void
huge_dalloc(void *ptr)
{
extent_node_t *node, key;
malloc_mutex_lock(&huge_mtx);
/* Extract from tree of huge allocations. */
key.addr = ptr;
node = extent_tree_ad_search(&huge, &key);
assert(node != NULL);
assert(node->addr == ptr);
extent_tree_ad_remove(&huge, node);
malloc_mutex_unlock(&huge_mtx);
huge_dalloc_junk(node->addr, node->size);
arena_chunk_dalloc_huge(node->arena, node->addr, node->size);
base_node_dalloc(node);
}
size_t
huge_salloc(const void *ptr)
{
size_t ret;
extent_node_t *node, key;
malloc_mutex_lock(&huge_mtx);
/* Extract from tree of huge allocations. */
key.addr = __DECONST(void *, ptr);
node = extent_tree_ad_search(&huge, &key);
assert(node != NULL);
ret = node->size;
malloc_mutex_unlock(&huge_mtx);
return (ret);
}
prof_tctx_t *
huge_prof_tctx_get(const void *ptr)
{
prof_tctx_t *ret;
extent_node_t *node, key;
malloc_mutex_lock(&huge_mtx);
/* Extract from tree of huge allocations. */
key.addr = __DECONST(void *, ptr);
node = extent_tree_ad_search(&huge, &key);
assert(node != NULL);
ret = node->prof_tctx;
malloc_mutex_unlock(&huge_mtx);
return (ret);
}
void
huge_prof_tctx_set(const void *ptr, prof_tctx_t *tctx)
{
extent_node_t *node, key;
malloc_mutex_lock(&huge_mtx);
/* Extract from tree of huge allocations. */
key.addr = __DECONST(void *, ptr);
node = extent_tree_ad_search(&huge, &key);
assert(node != NULL);
node->prof_tctx = tctx;
malloc_mutex_unlock(&huge_mtx);
}
bool
huge_boot(void)
{
/* Initialize chunks data. */
if (malloc_mutex_init(&huge_mtx))
return (true);
extent_tree_ad_new(&huge);
return (false);
}
void
huge_prefork(void)
{
malloc_mutex_prefork(&huge_mtx);
}
void
huge_postfork_parent(void)
{
malloc_mutex_postfork_parent(&huge_mtx);
}
void
huge_postfork_child(void)
{
malloc_mutex_postfork_child(&huge_mtx);
}