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Use first-fit rather than first-best-fit run/chunk allocation.

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This tends to more effectively pack active memory toward low addresses.
However, additional tree searches are required in many cases, so whether
this change stands the test of time will depend on real-world
benchmarks.
This commit is contained in:
Jason Evans 2015-03-06 19:57:36 -08:00
parent 5707d6f952
commit 97c04a9383
3 changed files with 89 additions and 32 deletions
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76
src/arena.c
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@ -907,23 +907,55 @@ arena_chunk_ralloc_huge_expand(arena_t *arena, void *chunk, size_t oldsize,
return (err);
}
/* Do first-fit run selection. */
static arena_run_t *
arena_run_first_fit(arena_t *arena, size_t size)
{
arena_run_t *run;
index_t index, max_index;
assert(size == s2u(size));
assert(size == PAGE_CEILING(size));
/*
* Iterate over all size classes that are at least large enough to
* satisfy the request, search for the lowest run of each size class,
* and choose the lowest of the runs found.
*/
run = NULL;
for (index = size2index(size), max_index = size2index(arena_maxclass);
index <= max_index;) {
arena_run_t *currun;
arena_chunk_t *currun_chunk;
size_t currun_pageind, currun_size;
size_t usize = PAGE_CEILING(index2size(index));
arena_chunk_map_misc_t *key = (arena_chunk_map_misc_t *)(usize |
CHUNK_MAP_KEY);
arena_chunk_map_misc_t *miscelm =
arena_avail_tree_nsearch(&arena->runs_avail, key);
if (miscelm == NULL)
break;
currun = &miscelm->run;
if (run == NULL || (uintptr_t)currun < (uintptr_t)run)
run = currun;
currun_chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(currun);
currun_pageind = arena_miscelm_to_pageind(miscelm);
currun_size = arena_mapbits_unallocated_size_get(currun_chunk,
currun_pageind);
assert(size2index(currun_size) + 1 > index);
index = size2index(currun_size) + 1;
}
return (run);
}
static arena_run_t *
arena_run_alloc_large_helper(arena_t *arena, size_t size, bool zero)
{
arena_chunk_map_misc_t *miscelm;
arena_chunk_map_misc_t *key;
size_t usize;
usize = s2u(size);
key = (arena_chunk_map_misc_t *)(usize | CHUNK_MAP_KEY);
miscelm = arena_avail_tree_nsearch(&arena->runs_avail, key);
if (miscelm != NULL) {
arena_run_t *run = &miscelm->run;
arena_run_split_large(arena, &miscelm->run, size, zero);
return (run);
}
return (NULL);
arena_run_t *run = arena_run_first_fit(arena, s2u(size));
if (run != NULL)
arena_run_split_large(arena, run, size, zero);
return (run);
}
static arena_run_t *
@ -961,20 +993,10 @@ arena_run_alloc_large(arena_t *arena, size_t size, bool zero)
static arena_run_t *
arena_run_alloc_small_helper(arena_t *arena, size_t size, index_t binind)
{
arena_run_t *run;
arena_chunk_map_misc_t *miscelm;
arena_chunk_map_misc_t *key;
assert(size == s2u(size));
key = (arena_chunk_map_misc_t *)(PAGE_CEILING(size) | CHUNK_MAP_KEY);
miscelm = arena_avail_tree_nsearch(&arena->runs_avail, key);
if (miscelm != NULL) {
run = &miscelm->run;
arena_run_t *run = arena_run_first_fit(arena, PAGE_CEILING(size));
if (run != NULL)
arena_run_split_small(arena, run, size, binind);
return (run);
}
return (NULL);
return (run);
}
static arena_run_t *