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Optimize arena_bin_pop() to reduce the number of separator operations.

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Remove the block of code that tries to use delayed regions in LIFO order,
since from a policy perspective, it conflicts with LRU caching of newly
coalesced regions in arena_undelay().  There are numerous policy
alternatives, and it isn't readily obvious which (if any) is superior;
this change at least has the virtue of being consistent with policy.
This commit is contained in:
Jason Evans 2006-01-26 08:11:23 +00:00
parent 6c4266852d
commit 499168546f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=154853
1 changed files with 10 additions and 13 deletions
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23
lib/libc/stdlib/malloc.c
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@ -2121,16 +2121,6 @@ arena_bin_pop(arena_t *arena, unsigned bin)
ret = qr_next(&tbin->regions, next.u.s.link);
assert(region_next_size_get(&ret->sep)
== ((bin + bin_shift) << opt_quantum_2pow));
if (region_next_free_get(&ret->sep) == false) {
/*
* Use delayed regions in LIFO order, in order to increase
* locality of use, and thereby (hopefully) reduce
* fragmentation.
*/
ret = qr_prev(&tbin->regions, next.u.s.link);
assert(region_next_size_get(&ret->sep)
== ((bin + bin_shift) << opt_quantum_2pow));
}
qr_remove(ret, next.u.s.link);
#ifdef MALLOC_STATS
arena->stats.bins[bin].nregions--;
@ -2138,9 +2128,16 @@ arena_bin_pop(arena_t *arena, unsigned bin)
if (qr_next(&tbin->regions, next.u.s.link) == &tbin->regions)
arena_mask_unset(arena, bin);
arena_delayed_extract(arena, ret);
if (region_next_free_get(&ret->sep) == false) {
uint32_t slot;
if (region_next_free_get(&ret->sep)) {
assert(region_next_contig_get(&ret->sep));
/* Extract this region from the delayed FIFO. */
slot = ret->next.u.s.slot;
assert(arena->delayed[slot] == ret);
arena->delayed[slot] = NULL;
} else {
region_t *next;
/* Non-delayed region. */
@ -2338,7 +2335,7 @@ arena_undelay(arena_t *arena, uint32_t slot)
- (CHUNK_REG_OFFSET + offsetof(region_t, next))) {
/*
* Insert coalesced region into appropriate bin (or
* largeRegions).
* large_regions).
*/
arena_lru_cache(arena, reg);
} else {