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Revert to first-best-fit run/chunk allocation.

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This effectively reverts 97c04a9383 (Use
first-fit rather than first-best-fit run/chunk allocation.).  In some
pathological cases, first-fit search dominates allocation time, and it
also tends not to converge as readily on a steady state of memory
layout, since precise allocation order has a bigger effect than for
first-best-fit.
This commit is contained in:
Jason Evans
2015-07-15 16:02:21 -07:00
parent 8693a9ea05
commit aa2826621e
3 changed files with 26 additions and 77 deletions
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44
src/chunk.c
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@@ -62,46 +62,20 @@ chunk_deregister(const void *chunk, const extent_node_t *node)
}
}
/* Do first-fit chunk selection. */
/*
* Do first-best-fit chunk selection, i.e. select the lowest chunk that best
* fits.
*/
static extent_node_t *
chunk_first_fit(arena_t *arena, extent_tree_t *chunks_szad,
chunk_first_best_fit(arena_t *arena, extent_tree_t *chunks_szad,
extent_tree_t *chunks_ad, size_t size)
{
extent_node_t *node;
index_t index;
extent_node_t key;
assert(size == CHUNK_CEILING(size));
if (size == chunksize) {
/*
* Any chunk will suffice, so simply select the one lowest in
* memory.
*/
return (extent_tree_ad_first(chunks_ad));
}
/*
* Iterate over all size classes that are at least large enough to
* satisfy the request, search for the lowest chunk of each size class,
* and choose the lowest of the chunks found.
*/
node = NULL;
for (index = size2index(size); index < NSIZES;) {
extent_node_t *curnode;
extent_node_t key;
extent_node_init(&key, arena, NULL,
CHUNK_CEILING(index2size(index)), false);
curnode = extent_tree_szad_nsearch(chunks_szad, &key);
if (curnode == NULL)
break;
if (node == NULL || (uintptr_t)extent_node_addr_get(curnode) <
(uintptr_t)extent_node_addr_get(node))
node = curnode;
assert(size2index(extent_node_size_get(curnode)) + 1 > index);
index = size2index(extent_node_size_get(curnode)) + 1;
}
return (node);
extent_node_init(&key, arena, NULL, size, false);
return (extent_tree_szad_nsearch(chunks_szad, &key));
}
static void *
@@ -127,7 +101,7 @@ chunk_recycle(arena_t *arena, extent_tree_t *chunks_szad,
extent_node_init(&key, arena, new_addr, alloc_size, false);
node = extent_tree_ad_search(chunks_ad, &key);
} else {
node = chunk_first_fit(arena, chunks_szad, chunks_ad,
node = chunk_first_best_fit(arena, chunks_szad, chunks_ad,
alloc_size);
}
if (node == NULL || (new_addr != NULL && extent_node_size_get(node) <