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In arena_chunk_reg_alloc(), try to avoid touching the last page in the

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chunk during initialization, in order to avoid physically backing the
page unless data are allocated there.
This commit is contained in:
Jason Evans 2006-01-23 03:19:01 +00:00
parent a9bf5e37ae
commit 5531d7fdc6
1 changed files with 24 additions and 7 deletions
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31
lib/libc/stdlib/malloc.c
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@ -2980,7 +2980,7 @@ RETURN:
static region_t *
arena_chunk_reg_alloc(arena_t *arena, size_t size, bool fit)
{
region_t *ret, *next;
region_t *ret;
chunk_node_t *chunk;
chunk = chunk_alloc(chunk_size);
@ -3014,12 +3014,29 @@ arena_chunk_reg_alloc(arena_t *arena, size_t size, bool fit)
region_prev_free_unset(&ret->sep);
region_next_free_unset(&ret->sep);
/* Create a separator at the end of this new region. */
next = (region_t *)&((char *)ret)[region_next_size_get(&ret->sep)];
region_next_size_set(&next->sep, 0);
region_prev_free_unset(&next->sep);
region_next_free_unset(&next->sep);
region_next_contig_unset(&next->sep);
/*
* Avoiding the following when possible is worthwhile, because it
* avoids touching a page that for many applications would never be
* touched otherwise.
*/
#ifdef USE_BRK
if ((uintptr_t)ret >= (uintptr_t)brk_base
&& (uintptr_t)ret < (uintptr_t)brk_max) {
region_t *next;
/*
* This may be a re-used brk chunk, so we have no guarantee
* that the memory is zero-filled. Therefore manually create a
* separator at the end of this new region (all zero bits).
*/
next = (region_t *)&((char *)ret)[region_next_size_get(
&ret->sep)];
region_next_size_set(&next->sep, 0);
region_prev_free_unset(&next->sep);
region_next_free_unset(&next->sep);
region_next_contig_unset(&next->sep);
}
#endif
if (fit)
arena_reg_fit(arena, size, ret, (arena->split == NULL));