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Perform delayed coalescing prior to purging.

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Rather than purging uncoalesced extents, perform just enough incremental
coalescing to purge only fully coalesced extents.  In the absence of
cached extent reuse, the immediate versus delayed incremental purging
algorithms result in the same purge order.

This resolves #655.
This commit is contained in:
Jason Evans 2017-03-02 18:04:35 -08:00
parent 8547ee11c3
commit e201e24904
6 changed files with 152 additions and 50 deletions
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28
src/arena.c
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@ -715,9 +715,9 @@ arena_stash_dirty(tsdn_t *tsdn, arena_t *arena, extent_hooks_t **r_extent_hooks,
/* Stash extents according to ndirty_limit. */
size_t nstashed = 0;
for (extent_t *extent = extents_evict(tsdn, &arena->extents_cached,
ndirty_limit); extent != NULL; extent = extents_evict(tsdn,
&arena->extents_cached, ndirty_limit)) {
extent_t *extent;
while ((extent = extents_evict(tsdn, arena, r_extent_hooks,
&arena->extents_cached, ndirty_limit)) != NULL) {
extent_list_append(purge_extents, extent);
nstashed += extent_size_get(extent) >> LG_PAGE;
}
@ -943,9 +943,9 @@ arena_destroy_retained(tsdn_t *tsdn, arena_t *arena) {
* either unmap retained extents or track them for later use.
*/
extent_hooks_t *extent_hooks = extent_hooks_get(arena);
for (extent_t *extent = extents_evict(tsdn, &arena->extents_retained,
0); extent != NULL; extent = extents_evict(tsdn,
&arena->extents_retained, 0)) {
extent_t *extent;
while ((extent = extents_evict(tsdn, arena, &extent_hooks,
&arena->extents_retained, 0)) != NULL) {
extent_dalloc_wrapper_try(tsdn, arena, &extent_hooks, extent);
}
}
@ -1679,12 +1679,24 @@ arena_new(tsdn_t *tsdn, unsigned ind, extent_hooks_t *extent_hooks) {
goto label_error;
}
/*
* Delay coalescing for cached extents despite the disruptive effect on
* memory layout for best-fit extent allocation, since cached extents
* are likely to be reused soon after deallocation, and the cost of
* merging/splitting extents is non-trivial.
*/
if (extents_init(tsdn, &arena->extents_cached, extent_state_dirty,
false)) {
true)) {
goto label_error;
}
/*
* Coalesce retained extents immediately, in part because they will
* never be evicted (and therefore there's no opportunity for delayed
* coalescing), but also because operations on retained extents are not
* in the critical path.
*/
if (extents_init(tsdn, &arena->extents_retained,
extent_state_retained, true)) {
extent_state_retained, false)) {
goto label_error;
}