Perform delayed coalescing prior to purging.
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
28
src/arena.c
28
src/arena.c
@@ -715,9 +715,9 @@ arena_stash_dirty(tsdn_t *tsdn, arena_t *arena, extent_hooks_t **r_extent_hooks,
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/* Stash extents according to ndirty_limit. */
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size_t nstashed = 0;
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for (extent_t *extent = extents_evict(tsdn, &arena->extents_cached,
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ndirty_limit); extent != NULL; extent = extents_evict(tsdn,
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&arena->extents_cached, ndirty_limit)) {
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extent_t *extent;
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while ((extent = extents_evict(tsdn, arena, r_extent_hooks,
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&arena->extents_cached, ndirty_limit)) != NULL) {
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extent_list_append(purge_extents, extent);
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nstashed += extent_size_get(extent) >> LG_PAGE;
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}
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@@ -943,9 +943,9 @@ arena_destroy_retained(tsdn_t *tsdn, arena_t *arena) {
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* either unmap retained extents or track them for later use.
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*/
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extent_hooks_t *extent_hooks = extent_hooks_get(arena);
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for (extent_t *extent = extents_evict(tsdn, &arena->extents_retained,
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0); extent != NULL; extent = extents_evict(tsdn,
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&arena->extents_retained, 0)) {
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extent_t *extent;
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while ((extent = extents_evict(tsdn, arena, &extent_hooks,
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&arena->extents_retained, 0)) != NULL) {
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extent_dalloc_wrapper_try(tsdn, arena, &extent_hooks, extent);
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}
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}
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@@ -1679,12 +1679,24 @@ arena_new(tsdn_t *tsdn, unsigned ind, extent_hooks_t *extent_hooks) {
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goto label_error;
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}
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/*
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* Delay coalescing for cached extents despite the disruptive effect on
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* memory layout for best-fit extent allocation, since cached extents
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* are likely to be reused soon after deallocation, and the cost of
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* merging/splitting extents is non-trivial.
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*/
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if (extents_init(tsdn, &arena->extents_cached, extent_state_dirty,
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false)) {
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true)) {
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goto label_error;
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}
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/*
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* Coalesce retained extents immediately, in part because they will
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* never be evicted (and therefore there's no opportunity for delayed
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* coalescing), but also because operations on retained extents are not
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* in the critical path.
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*/
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if (extents_init(tsdn, &arena->extents_retained,
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extent_state_retained, true)) {
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extent_state_retained, false)) {
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goto label_error;
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}
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151
src/extent.c
151
src/extent.c
@@ -69,6 +69,9 @@ static size_t highpages;
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*/
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static void extent_deregister(tsdn_t *tsdn, extent_t *extent);
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static extent_t *extent_try_coalesce(tsdn_t *tsdn, arena_t *arena,
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extent_hooks_t **r_extent_hooks, rtree_ctx_t *rtree_ctx, extents_t *extents,
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extent_t *extent, bool *coalesced);
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static void extent_record(tsdn_t *tsdn, arena_t *arena,
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extent_hooks_t **r_extent_hooks, extents_t *extents, extent_t *extent);
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@@ -175,7 +178,7 @@ ph_gen(, extent_heap_, extent_heap_t, extent_t, ph_link, extent_snad_comp)
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bool
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extents_init(tsdn_t *tsdn, extents_t *extents, extent_state_t state,
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bool try_coalesce) {
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bool delay_coalesce) {
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if (malloc_mutex_init(&extents->mtx, "extents", WITNESS_RANK_EXTENTS)) {
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return true;
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}
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@@ -185,7 +188,7 @@ extents_init(tsdn_t *tsdn, extents_t *extents, extent_state_t state,
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extent_list_init(&extents->lru);
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extents->npages = 0;
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extents->state = state;
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extents->try_coalesce = try_coalesce;
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extents->delay_coalesce = delay_coalesce;
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return false;
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}
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@@ -200,7 +203,8 @@ extents_npages_get(extents_t *extents) {
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}
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static void
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extents_insert_locked(tsdn_t *tsdn, extents_t *extents, extent_t *extent) {
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extents_insert_locked(tsdn_t *tsdn, extents_t *extents, extent_t *extent,
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bool preserve_lru) {
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malloc_mutex_assert_owner(tsdn, &extents->mtx);
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assert(extent_state_get(extent) == extents->state);
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@@ -208,13 +212,16 @@ extents_insert_locked(tsdn_t *tsdn, extents_t *extents, extent_t *extent) {
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size_t psz = extent_size_quantize_floor(size);
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pszind_t pind = psz2ind(psz);
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extent_heap_insert(&extents->heaps[pind], extent);
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extent_list_append(&extents->lru, extent);
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if (!preserve_lru) {
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extent_list_append(&extents->lru, extent);
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}
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size_t npages = size >> LG_PAGE;
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atomic_add_zu(&extents->npages, npages);
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}
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static void
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extents_remove_locked(tsdn_t *tsdn, extents_t *extents, extent_t *extent) {
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extents_remove_locked(tsdn_t *tsdn, extents_t *extents, extent_t *extent,
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bool preserve_lru) {
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malloc_mutex_assert_owner(tsdn, &extents->mtx);
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assert(extent_state_get(extent) == extents->state);
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@@ -222,7 +229,9 @@ extents_remove_locked(tsdn_t *tsdn, extents_t *extents, extent_t *extent) {
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size_t psz = extent_size_quantize_floor(size);
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pszind_t pind = psz2ind(psz);
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extent_heap_remove(&extents->heaps[pind], extent);
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extent_list_remove(&extents->lru, extent);
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if (!preserve_lru) {
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extent_list_remove(&extents->lru, extent);
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}
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size_t npages = size >> LG_PAGE;
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assert(atomic_read_zu(&extents->npages) >= npages);
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atomic_sub_zu(&extents->npages, size >> LG_PAGE);
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@@ -249,22 +258,62 @@ extents_first_best_fit_locked(tsdn_t *tsdn, arena_t *arena, extents_t *extents,
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return NULL;
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}
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static bool
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extent_try_delayed_coalesce(tsdn_t *tsdn, arena_t *arena,
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extent_hooks_t **r_extent_hooks, rtree_ctx_t *rtree_ctx, extents_t *extents,
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extent_t *extent) {
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extent_state_set(extent, extent_state_active);
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bool coalesced;
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extent = extent_try_coalesce(tsdn, arena, r_extent_hooks, rtree_ctx,
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extents, extent, &coalesced);
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extent_state_set(extent, extents_state_get(extents));
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if (!coalesced) {
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return true;
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}
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extents_insert_locked(tsdn, extents, extent, true);
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return false;
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}
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extent_t *
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extents_evict(tsdn_t *tsdn, extents_t *extents, size_t npages_min) {
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extents_evict(tsdn_t *tsdn, arena_t *arena, extent_hooks_t **r_extent_hooks,
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extents_t *extents, size_t npages_min) {
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rtree_ctx_t rtree_ctx_fallback;
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rtree_ctx_t *rtree_ctx = tsdn_rtree_ctx(tsdn, &rtree_ctx_fallback);
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malloc_mutex_lock(tsdn, &extents->mtx);
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/* Get the LRU extent, if any. */
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extent_t *extent = extent_list_first(&extents->lru);
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if (extent == NULL) {
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goto label_return;
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/*
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* Get the LRU coalesced extent, if any. If coalescing was delayed,
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* the loop will iterate until the LRU extent is fully coalesced.
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*/
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extent_t *extent;
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while (true) {
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/* Get the LRU extent, if any. */
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extent = extent_list_first(&extents->lru);
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if (extent == NULL) {
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goto label_return;
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}
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/* Check the eviction limit. */
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size_t npages = extent_size_get(extent) >> LG_PAGE;
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if (atomic_read_zu(&extents->npages) - npages < npages_min) {
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extent = NULL;
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goto label_return;
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}
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extents_remove_locked(tsdn, extents, extent, false);
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if (!extents->delay_coalesce) {
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break;
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}
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/* Try to coalesce. */
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if (extent_try_delayed_coalesce(tsdn, arena, r_extent_hooks,
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rtree_ctx, extents, extent)) {
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break;
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}
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/*
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* The LRU extent was just coalesced and the result placed in
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* the LRU at its neighbor's position. Start over.
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*/
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}
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/* Check the eviction limit. */
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size_t npages = extent_size_get(extent) >> LG_PAGE;
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if (atomic_read_zu(&extents->npages) - npages < npages_min) {
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extent = NULL;
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goto label_return;
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}
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extents_remove_locked(tsdn, extents, extent);
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/*
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* Either mark the extent active or deregister it to protect against
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@@ -320,29 +369,29 @@ extents_postfork_child(tsdn_t *tsdn, extents_t *extents) {
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static void
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extent_deactivate_locked(tsdn_t *tsdn, arena_t *arena, extents_t *extents,
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extent_t *extent) {
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extent_t *extent, bool preserve_lru) {
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assert(extent_arena_get(extent) == arena);
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assert(extent_state_get(extent) == extent_state_active);
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extent_state_set(extent, extents_state_get(extents));
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extents_insert_locked(tsdn, extents, extent);
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extents_insert_locked(tsdn, extents, extent, preserve_lru);
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}
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static void
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extent_deactivate(tsdn_t *tsdn, arena_t *arena, extents_t *extents,
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extent_t *extent) {
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extent_t *extent, bool preserve_lru) {
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malloc_mutex_lock(tsdn, &extents->mtx);
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extent_deactivate_locked(tsdn, arena, extents, extent);
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extent_deactivate_locked(tsdn, arena, extents, extent, preserve_lru);
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malloc_mutex_unlock(tsdn, &extents->mtx);
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}
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static void
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extent_activate_locked(tsdn_t *tsdn, arena_t *arena, extents_t *extents,
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extent_t *extent) {
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extent_t *extent, bool preserve_lru) {
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assert(extent_arena_get(extent) == arena);
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assert(extent_state_get(extent) == extents_state_get(extents));
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extents_remove_locked(tsdn, extents, extent);
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extents_remove_locked(tsdn, extents, extent, preserve_lru);
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extent_state_set(extent, extent_state_active);
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}
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@@ -581,7 +630,7 @@ extent_recycle_extract(tsdn_t *tsdn, arena_t *arena,
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return NULL;
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}
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extent_activate_locked(tsdn, arena, extents, extent);
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extent_activate_locked(tsdn, arena, extents, extent, false);
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if (!locked) {
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malloc_mutex_unlock(tsdn, &extents->mtx);
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}
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@@ -620,7 +669,7 @@ extent_recycle_split(tsdn_t *tsdn, arena_t *arena,
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lead);
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return NULL;
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}
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extent_deactivate(tsdn, arena, extents, lead);
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extent_deactivate(tsdn, arena, extents, lead, false);
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}
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/* Split the trail. */
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@@ -633,7 +682,7 @@ extent_recycle_split(tsdn_t *tsdn, arena_t *arena,
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extent);
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return NULL;
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}
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extent_deactivate(tsdn, arena, extents, trail);
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extent_deactivate(tsdn, arena, extents, trail, false);
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} else if (leadsize == 0) {
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/*
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* Splitting causes usize to be set as a side effect, but no
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@@ -1030,7 +1079,16 @@ extent_coalesce(tsdn_t *tsdn, arena_t *arena, extent_hooks_t **r_extent_hooks,
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extents_t *extents, extent_t *inner, extent_t *outer, bool forward) {
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assert(extent_can_coalesce(arena, extents, inner, outer));
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extent_activate_locked(tsdn, arena, extents, outer);
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if (forward && extents->delay_coalesce) {
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/*
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* The extent that remains after coalescing must occupy the
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* outer extent's position in the LRU. For forward coalescing,
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* swap the inner extent into the LRU.
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*/
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extent_list_replace(&extents->lru, outer, inner);
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}
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extent_activate_locked(tsdn, arena, extents, outer,
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extents->delay_coalesce);
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malloc_mutex_unlock(tsdn, &extents->mtx);
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bool err = extent_merge_wrapper(tsdn, arena, r_extent_hooks,
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@@ -1038,7 +1096,11 @@ extent_coalesce(tsdn_t *tsdn, arena_t *arena, extent_hooks_t **r_extent_hooks,
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malloc_mutex_lock(tsdn, &extents->mtx);
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if (err) {
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extent_deactivate_locked(tsdn, arena, extents, outer);
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if (forward && extents->delay_coalesce) {
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extent_list_replace(&extents->lru, inner, outer);
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}
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extent_deactivate_locked(tsdn, arena, extents, outer,
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extents->delay_coalesce);
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}
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return err;
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@@ -1047,14 +1109,14 @@ extent_coalesce(tsdn_t *tsdn, arena_t *arena, extent_hooks_t **r_extent_hooks,
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static extent_t *
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extent_try_coalesce(tsdn_t *tsdn, arena_t *arena,
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extent_hooks_t **r_extent_hooks, rtree_ctx_t *rtree_ctx, extents_t *extents,
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extent_t *extent) {
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extent_t *extent, bool *coalesced) {
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/*
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* Continue attempting to coalesce until failure, to protect against
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* races with other threads that are thwarted by this one.
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*/
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bool coalesced;
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bool again;
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do {
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coalesced = false;
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again = false;
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/* Try to coalesce forward. */
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rtree_elm_t *next_elm = rtree_elm_acquire(tsdn, &extents_rtree,
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@@ -1073,7 +1135,12 @@ extent_try_coalesce(tsdn_t *tsdn, arena_t *arena,
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rtree_elm_release(tsdn, &extents_rtree, next_elm);
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if (can_coalesce && !extent_coalesce(tsdn, arena,
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r_extent_hooks, extents, extent, next, true)) {
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coalesced = true;
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if (extents->delay_coalesce) {
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/* Do minimal coalescing. */
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*coalesced = true;
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return extent;
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}
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again = true;
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}
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}
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@@ -1090,11 +1157,19 @@ extent_try_coalesce(tsdn_t *tsdn, arena_t *arena,
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if (can_coalesce && !extent_coalesce(tsdn, arena,
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r_extent_hooks, extents, extent, prev, false)) {
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extent = prev;
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coalesced = true;
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if (extents->delay_coalesce) {
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/* Do minimal coalescing. */
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*coalesced = true;
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return extent;
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}
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again = true;
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}
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}
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} while (coalesced);
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} while (again);
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if (extents->delay_coalesce) {
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*coalesced = false;
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}
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return extent;
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}
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@@ -1118,12 +1193,12 @@ extent_record(tsdn_t *tsdn, arena_t *arena, extent_hooks_t **r_extent_hooks,
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assert(extent_lookup(tsdn, extent_base_get(extent), true) == extent);
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if (extents->try_coalesce) {
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if (!extents->delay_coalesce) {
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extent = extent_try_coalesce(tsdn, arena, r_extent_hooks,
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rtree_ctx, extents, extent);
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rtree_ctx, extents, extent, NULL);
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}
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extent_deactivate_locked(tsdn, arena, extents, extent);
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extent_deactivate_locked(tsdn, arena, extents, extent, false);
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malloc_mutex_unlock(tsdn, &extents->mtx);
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}
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