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Ehooks: Further optimize default merge case.

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This avoids the cost of an iealloc in cases where the user uses the default
merge hook without using the default extent hooks.
This commit is contained in:
David Goldblatt 2019-12-19 17:53:52 -08:00 committed by David Goldblatt
parent f2f2084e79
commit 6342da0970
2 changed files with 19 additions and 2 deletions
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19
include/jemalloc/internal/ehooks.h
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@ -54,6 +54,13 @@ bool ehooks_default_purge_lazy_impl(void *addr, size_t offset, size_t length);
bool ehooks_default_purge_forced_impl(void *addr, size_t offset, size_t length);
#endif
bool ehooks_default_split_impl();
/*
* Merge is the only default extent hook we declare -- see the comment in
* ehooks_merge.
*/
bool ehooks_default_merge(extent_hooks_t *extent_hooks, void *addr_a,
size_t size_a, void *addr_b, size_t size_b, bool committed,
unsigned arena_ind);
bool ehooks_default_merge_impl(tsdn_t *tsdn, void *addr_a, bool head_a,
void *addr_b, bool head_b);
void ehooks_default_zero_impl(void *addr, size_t size);
@ -333,7 +340,17 @@ static inline bool
ehooks_merge(tsdn_t *tsdn, ehooks_t *ehooks, void *addr_a, size_t size_a,
bool head_a, void *addr_b, size_t size_b, bool head_b, bool committed) {
extent_hooks_t *extent_hooks = ehooks_get_extent_hooks_ptr(ehooks);
if (extent_hooks == &ehooks_default_extent_hooks) {
/*
* The definition of extent_hooks merge function doesn't know about
* extent head state, but the implementation does. As a result, it
* needs to call iealloc again and walk the rtree. Since the cost of an
* iealloc is large relative to the cost of the default merge hook
* (which on posix-likes is just "return false"), we go even further
* when we short-circuit; we don't just check if the extent hooks
* generally are default, we check if the merge hook specifically is.
*/
if (extent_hooks == &ehooks_default_extent_hooks
|| extent_hooks->merge == &ehooks_default_merge) {
return ehooks_default_merge_impl(tsdn, addr_a, head_a, addr_b,
head_b);
} else if (extent_hooks->merge == NULL) {

2
src/ehooks.c
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@ -242,7 +242,7 @@ ehooks_default_merge_impl(tsdn_t *tsdn, void *addr_a, bool head_a, void *addr_b,
return false;
}
static bool
bool
ehooks_default_merge(extent_hooks_t *extent_hooks, void *addr_a, size_t size_a,
void *addr_b, size_t size_b, bool committed, unsigned arena_ind) {
tsdn_t *tsdn = tsdn_fetch();