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Only initialize the first per-chunk page map element for free runs. This

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makes run split/coalesce operations of complexity lg(n) rather than n.
This commit is contained in:
Jason Evans 2006-04-05 04:15:12 +00:00
parent 1f65c2cd31
commit 50ff9670e2
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=157532
1 changed files with 16 additions and 31 deletions
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47
lib/libc/stdlib/malloc.c
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@ -1639,14 +1639,9 @@ arena_run_split(arena_t *arena, arena_run_t *run, bool large, size_t size)
total_pages = chunk->map[run_ind].npages;
need_pages = (size >> pagesize_2pow);
#ifdef MALLOC_DEBUG
for (i = 0; i < total_pages; i++) {
assert(chunk->map[run_ind + i].free);
assert(chunk->map[run_ind + i].large == false);
assert(chunk->map[run_ind + i].npages == total_pages);
assert(chunk->map[run_ind + i].pos == i);
}
#endif
assert(chunk->map[run_ind].free);
assert(chunk->map[run_ind].large == false);
assert(chunk->map[run_ind].npages == total_pages);
/* Split enough pages from the front of run to fit allocation size. */
map_offset = run_ind;
@ -1662,12 +1657,10 @@ arena_run_split(arena_t *arena, arena_run_t *run, bool large, size_t size)
while (map_offset < run_ind + total_pages) {
log2_run_pages = ffs(map_offset) - 1;
run_pages = (1 << log2_run_pages);
for (i = 0; i < run_pages; i++) {
chunk->map[map_offset + i].free = true;
chunk->map[map_offset + i].large = false;
chunk->map[map_offset + i].npages = run_pages;
chunk->map[map_offset + i].pos = i;
}
chunk->map[map_offset].free = true;
chunk->map[map_offset].large = false;
chunk->map[map_offset].npages = run_pages;
chunk->nfree_runs[log2_run_pages]++;
@ -1737,12 +1730,10 @@ arena_chunk_alloc(arena_t *arena)
while (map_offset < (chunk_size >> pagesize_2pow)) {
log2_run_pages = ffs(map_offset) - 1;
run_pages = (1 << log2_run_pages);
for (i = 0; i < run_pages; i++) {
chunk->map[map_offset + i].free = true;
chunk->map[map_offset + i].large = false;
chunk->map[map_offset + i].npages = run_pages;
chunk->map[map_offset + i].pos = i;
}
chunk->map[map_offset].free = true;
chunk->map[map_offset].large = false;
chunk->map[map_offset].npages = run_pages;
chunk->nfree_runs[log2_run_pages]++;
@ -1970,7 +1961,7 @@ static void
arena_run_dalloc(arena_t *arena, arena_run_t *run, size_t size)
{
arena_chunk_t *chunk;
unsigned i, run_ind, buddy_ind, base_run_ind, run_pages, log2_run_pages;
unsigned run_ind, buddy_ind, base_run_ind, run_pages, log2_run_pages;
chunk = (arena_chunk_t *)CHUNK_ADDR2BASE(run);
run_ind = (unsigned)(((uintptr_t)run - (uintptr_t)chunk)
@ -1983,12 +1974,9 @@ arena_run_dalloc(arena_t *arena, arena_run_t *run, size_t size)
chunk->pages_used -= run_pages;
/* Mark run as deallocated. */
for (i = 0; i < run_pages; i++) {
chunk->map[run_ind + i].free = true;
chunk->map[run_ind + i].large = false;
chunk->map[run_ind + i].npages = run_pages;
chunk->map[run_ind + i].pos = i;
}
chunk->map[run_ind].free = true;
chunk->map[run_ind].large = false;
chunk->map[run_ind].npages = run_pages;
/*
* Tell the kernel that we don't need the data in this run, but only if
@ -2029,10 +2017,7 @@ arena_run_dalloc(arena_t *arena, arena_run_t *run, size_t size)
chunk->nfree_runs[log2_run_pages]--;
/* Coalesce. */
for (i = 0; i < (run_pages << 1); i++) {
chunk->map[base_run_ind + i].npages = (run_pages << 1);
chunk->map[base_run_ind + i].pos = i;
}
chunk->map[base_run_ind].npages = (run_pages << 1);
/* Update run_ind to be the beginning of the coalesced run. */
run_ind = base_run_ind;