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Move deferred-work orchestration from arena into pa/pac.

Browse source 
Move most arena-owned PAC deferral & background thread relevant codes
out to pa/pac for decoupling purposes.
This commit is contained in:
guangli-dai 2026-06-30 16:28:27 -07:00 • committed by Guangli Dai
parent e16ebfe27e
commit 01df5c96e0
5 changed files with 274 additions and 202 deletions
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36
include/jemalloc/internal/pa.h
View file

@ -152,8 +152,12 @@ void pa_shard_reset(tsdn_t *tsdn, pa_shard_t *shard);
*/
void pa_shard_destroy(tsdn_t *tsdn, pa_shard_t *shard);
/* Flush any caches used by shard */
void pa_shard_flush(tsdn_t *tsdn, pa_shard_t *shard);
/*
* Flush the shard's front caches (SEC + HPA) back to the ecaches. If all is
* true, also fully decay-purge the PAC dirty (and muzzy, unless skipped) extents
* to the OS -- the "save as much memory as possible" path.
*/
void pa_shard_flush(tsdn_t *tsdn, pa_shard_t *shard, bool all);
/* Gets an edata for the given allocation. */
edata_t *pa_alloc(tsdn_t *tsdn, pa_shard_t *shard, size_t size,
@ -178,21 +182,35 @@ bool pa_shrink(tsdn_t *tsdn, pa_shard_t *shard, edata_t *edata, size_t old_size,
void pa_dalloc(tsdn_t *tsdn, pa_shard_t *shard, edata_t *edata,
bool *deferred_work_generated);
bool pa_decay_ms_set(tsdn_t *tsdn, pa_shard_t *shard, extent_state_t state,
ssize_t decay_ms, pac_purge_eagerness_t eagerness);
ssize_t decay_ms);
ssize_t pa_decay_ms_get(pa_shard_t *shard, extent_state_t state);
/*
* Do deferred work on this PA shard: both PAC decay and the HPA deferred work
* symetrically. The only exception in the symetry is PAC decay-purge policy
* requires the eagerness, which is passed in from the arena.
*/
void pa_shard_set_deferral_allowed(
tsdn_t *tsdn, pa_shard_t *shard, bool deferral_allowed);
/*
* Do deferred work on this PA shard: dispatch to PAC (decay-purge) then HPA.
* Each allocator owns its own policy -- PAC decides eagerness from
* is_background_thread and, on the application path, notifies the background
* thread; the bg-thread driver passes is_background_thread=true and is never
* self-notified.
*/
void pa_shard_do_deferred_work(
tsdn_t *tsdn, pa_shard_t *shard, pac_purge_eagerness_t eagerness);
tsdn_t *tsdn, pa_shard_t *shard, bool is_background_thread);
void pa_shard_try_deferred_work(tsdn_t *tsdn, pa_shard_t *shard);
uint64_t pa_shard_time_until_deferred_work(tsdn_t *tsdn, pa_shard_t *shard);
/*
* Called on the application path after a pa operation (alloc/expand/shrink/
* dalloc) reports deferred_work_generated -- i.e. it left PAC decay due or
* HPA work (hugify/dehugify/purge) pending. If PAC dirty decay is immediate
* (dirty_decay_ms == 0), purge dirty synchronously; then, if a background
* thread is enabled but idle (sleeping indefinitely), wake it early so the
* pending work runs promptly rather than at the next scheduled wakeup.
*
* Application thread only; must never be called on the background thread.
*/
void pa_shard_handle_deferred_work(tsdn_t *tsdn, pa_shard_t *shard);
/******************************************************************************/
/*
* Various bits of "boring" functionality that are still part of this module,

33
include/jemalloc/internal/pac.h
View file

@ -240,10 +240,10 @@ bool pac_maybe_decay_purge(tsdn_t *tsdn, pac_t *pac, decay_t *decay,
pac_purge_eagerness_t eagerness);
/*
* Result of a pac_do_deferred_work() pass. Reported per decay state so the
* caller (on the user-inline path) can decide, per state, whether to notify the
* background thread. npages_new is the per-state epoch backlog delta, only
* meaningful when the corresponding *_epoch_advanced is true.
* Result of a pac_decay_deferred() pass. Reported per decay state so
* pac_do_deferred_work can decide, per state, whether to notify the background
* thread. npages_new is the per-state epoch backlog delta, only meaningful when
* the corresponding *_epoch_advanced is true.
*/
typedef struct pac_deferred_work_result_s pac_deferred_work_result_t;
struct pac_deferred_work_result_s {
@ -254,11 +254,20 @@ struct pac_deferred_work_result_s {
};
/*
* Non-forced deferred decay work for both the dirty and muzzy states.
* Corresponding decay->mtx are acquired internally.
* All deferred decay-purge work for a PAC shard: decide the eagerness from the
* caller context, run pac_decay_deferred, and (application path only) notify the
* background thread for any decay epoch that advanced. The bg-thread driver
* passes is_background_thread=true and is never self-notified.
*/
void pac_do_deferred_work(tsdn_t *tsdn, pac_t *pac,
pac_purge_eagerness_t eagerness, pac_deferred_work_result_t *result);
void pac_do_deferred_work(
tsdn_t *tsdn, pac_t *pac, bool is_background_thread);
/*
* Application-path hook (after deferred_work_generated): wake the background
* thread if it is sleeping idle. Runs the same early-wake logic as the notify
* path (pac_maybe_wake_bg), gated on the thread being idle.
*/
void pac_wake_bg_on_deferred(tsdn_t *tsdn, pac_t *pac);
/*
* Fully decay the extents of the given state, acquiring decay->mtx internally.
@ -278,7 +287,7 @@ bool pac_retain_grow_limit_get_set(
tsdn_t *tsdn, pac_t *pac, size_t *old_limit, size_t *new_limit);
bool pac_decay_ms_set(tsdn_t *tsdn, pac_t *pac, extent_state_t state,
ssize_t decay_ms, pac_purge_eagerness_t eagerness);
ssize_t decay_ms);
ssize_t pac_decay_ms_get(pac_t *pac, extent_state_t state);
/* Whether the muzzy decay path is relevant (muzzy pages exist, or decay is on). */
@ -288,6 +297,12 @@ pac_should_decay_muzzy(pac_t *pac) {
|| pac_decay_ms_get(pac, extent_state_muzzy) > 0;
}
/* Whether dirty decay is immediate (dirty_decay_ms == 0). */
static inline bool
pac_decay_immediately(pac_t *pac) {
return decay_immediately(&pac->decay_dirty);
}
void pac_destroy(tsdn_t *tsdn, pac_t *pac);
void pac_sec_flush(tsdn_t *tsdn, pac_t *pac);

186
src/arena.c
View file

@ -83,9 +83,6 @@ const arena_config_t arena_config_default = {
* definition.
*/
static void arena_maybe_do_deferred_work(
tsdn_t *tsdn, arena_t *arena, decay_t *decay, size_t npages_new);
/******************************************************************************/
void
@ -314,32 +311,13 @@ arena_cache_bins_stats_merge(tsdn_t *tsdn, arena_t *arena) {
malloc_mutex_unlock(tsdn, &arena->cache_bin_array_descriptor_ql_mtx);
}
static void
arena_background_thread_inactivity_check(
tsdn_t *tsdn, arena_t *arena, bool is_background_thread) {
if (!background_thread_enabled() || is_background_thread) {
return;
}
background_thread_info_t *info = arena_background_thread_info_get(
arena);
if (background_thread_indefinite_sleep(info)) {
arena_maybe_do_deferred_work(
tsdn, arena, &arena->pa_shard.pac.decay_dirty, 0);
}
}
/*
* React to deferred work generated by a PAI function.
* React to deferred work generated by a PAI function. Delegates to pa, which
* owns the PAC/HPA decay + background-thread interaction.
*/
void
arena_handle_deferred_work(tsdn_t *tsdn, arena_t *arena) {
witness_assert_depth_to_rank(
tsdn_witness_tsdp_get(tsdn), WITNESS_RANK_CORE, 0);
if (decay_immediately(&arena->pa_shard.pac.decay_dirty)) {
pac_decay_all_now(tsdn, &arena->pa_shard.pac, extent_state_dirty);
}
arena_background_thread_inactivity_check(tsdn, arena, false);
pa_shard_handle_deferred_work(tsdn, &arena->pa_shard);
}
static void
@ -474,29 +452,10 @@ arena_extent_ralloc_large_expand(
}
}
/*
* In situations where we're not forcing a decay (i.e. because the user
* specifically requested it), should we purge ourselves, or wait for the
* background thread to get to it.
*/
static pac_purge_eagerness_t
arena_decide_unforced_purge_eagerness(bool is_background_thread) {
if (is_background_thread) {
return PAC_PURGE_ALWAYS;
} else if (!is_background_thread && background_thread_enabled()) {
return PAC_PURGE_NEVER;
} else {
return PAC_PURGE_ON_EPOCH_ADVANCE;
}
}
bool
arena_decay_ms_set(
tsdn_t *tsdn, arena_t *arena, extent_state_t state, ssize_t decay_ms) {
pac_purge_eagerness_t eagerness = arena_decide_unforced_purge_eagerness(
/* is_background_thread */ false);
return pa_decay_ms_set(
tsdn, &arena->pa_shard, state, decay_ms, eagerness);
return pa_decay_ms_set(tsdn, &arena->pa_shard, state, decay_ms);
}
ssize_t
@ -508,144 +467,31 @@ void
arena_decay(tsdn_t *tsdn, arena_t *arena, bool is_background_thread, bool all) {
if (all) {
/*
* We should take a purge of "all" to mean "save as much memory
* as possible", including flushing any caches (for situations
* like thread death, or manual purge calls). This blocking
* flush-and-fully-decay path is kept separate from the deferred
* (all=false) path below.
* A purge of "all" means "save as much memory as possible"
* (thread death, manual purge): flush caches and fully decay.
*/
pa_shard_flush(tsdn, &arena->pa_shard);
pac_decay_all_now(
tsdn, &arena->pa_shard.pac, extent_state_dirty);
if (pac_should_decay_muzzy(&arena->pa_shard.pac)) {
pac_decay_all_now(
tsdn, &arena->pa_shard.pac, extent_state_muzzy);
}
pa_shard_flush(tsdn, &arena->pa_shard, /* all */ true);
return;
}
/*
* Deferred (non-forced) decay-purge. The PAC layer owns the decay
* orchestration (lock acquisition, dirty-before-muzzy ordering, the
* dirty-contended-skip-muzzy and muzzy short-circuit rules). We call
* it with the eagerness decided here and then notify the background
* thread per decay state for any epoch that advanced.
*
* A concurrent background_thread enable/disable (mallctl) can race
* this path: the enable state is read lock-free twice below (for the
* eagerness decision, then the notify guard), so the two reads may
* disagree. Worst case is benign and self-healing:
* disabled->enabled: purged immediately, plus a possibly-redundant
* wake;
* enabled->disabled: deferred but not notified this pass -- the
* pages stay in the decay backlog and are reclaimed on the next
* decay tick or by the bg thread before it stops.
* It stays safe regardless: info is allocated once and never freed;
* the wake is gated by info->mtx + background_thread_is_started() (so
* we never signal a not-yet-running thread); the bg-thread locks here
* are trylocks; and the purge runs under decay->mtx, which the toggle
* never touches.
* Deferred (non-forced) decay-purge: pa owns the whole bridge (eagerness
* decision, PAC decay orchestration, and background-thread notify).
*/
pac_purge_eagerness_t eagerness = arena_decide_unforced_purge_eagerness(
is_background_thread);
pac_deferred_work_result_t result;
pac_do_deferred_work(
tsdn, &arena->pa_shard.pac, eagerness, &result);
if (have_background_thread && background_thread_enabled()
&& !is_background_thread) {
if (result.dirty_epoch_advanced) {
arena_maybe_do_deferred_work(tsdn, arena,
&arena->pa_shard.pac.decay_dirty,
result.dirty_npages_new);
}
if (result.muzzy_epoch_advanced) {
arena_maybe_do_deferred_work(tsdn, arena,
&arena->pa_shard.pac.decay_muzzy,
result.muzzy_npages_new);
}
}
}
static bool
arena_should_decay_early(tsdn_t *tsdn, arena_t *arena, decay_t *decay,
background_thread_info_t *info, nstime_t *remaining_sleep,
size_t npages_new) {
malloc_mutex_assert_owner(tsdn, &info->mtx);
if (malloc_mutex_trylock(tsdn, &decay->mtx)) {
return false;
}
if (!decay_gradually(decay)) {
malloc_mutex_unlock(tsdn, &decay->mtx);
return false;
}
nstime_init(remaining_sleep, background_thread_wakeup_time_get(info));
if (nstime_compare(remaining_sleep, &decay->epoch) <= 0) {
malloc_mutex_unlock(tsdn, &decay->mtx);
return false;
}
nstime_subtract(remaining_sleep, &decay->epoch);
if (npages_new > 0) {
uint64_t npurge_new = decay_npages_purge_in(
decay, remaining_sleep, npages_new);
info->npages_to_purge_new += npurge_new;
}
malloc_mutex_unlock(tsdn, &decay->mtx);
return info->npages_to_purge_new
> PAC_DECAY_PURGE_NPAGES_THRESHOLD;
}
/*
* Check if deferred work needs to be done sooner than planned.
* For decay we might want to wake up earlier because of an influx of dirty
* pages. Rather than waiting for previously estimated time, we proactively
* purge those pages.
* If background thread sleeps indefinitely, always wake up because some
* deferred work has been generated.
*/
static void
arena_maybe_do_deferred_work(
tsdn_t *tsdn, arena_t *arena, decay_t *decay, size_t npages_new) {
background_thread_info_t *info = arena_background_thread_info_get(
arena);
if (malloc_mutex_trylock(tsdn, &info->mtx)) {
/*
* Background thread may hold the mutex for a long period of
* time. We'd like to avoid the variance on application
* threads. So keep this non-blocking, and leave the work to a
* future epoch.
*/
return;
}
if (!background_thread_is_started(info)) {
goto label_done;
}
nstime_t remaining_sleep;
if (background_thread_indefinite_sleep(info)) {
background_thread_wakeup_early(info, NULL);
} else if (arena_should_decay_early(tsdn, arena, decay, info,
&remaining_sleep, npages_new)) {
info->npages_to_purge_new = 0;
background_thread_wakeup_early(info, &remaining_sleep);
}
label_done:
malloc_mutex_unlock(tsdn, &info->mtx);
pa_shard_do_deferred_work(
tsdn, &arena->pa_shard, is_background_thread);
}
/* Called from background threads. */
void
arena_do_deferred_work(tsdn_t *tsdn, arena_t *arena) {
/*
* The background thread forces decay (PAC_PURGE_ALWAYS) and drives both
* PAC and HPA deferred work through the symmetric pa_shard facade. No
* PAC result is needed here to notify background thread for an early
* wake because this function should be called in background thread.
* Runs on the background thread. is_background_thread=true makes pa
* force the PAC purge (eagerness ALWAYS) and skip the early-wake --
* the background thread must not notify itself.
*/
pa_shard_do_deferred_work(tsdn, &arena->pa_shard, PAC_PURGE_ALWAYS);
pa_shard_do_deferred_work(
tsdn, &arena->pa_shard, /* is_background_thread */ true);
}
static void

41
src/pa.c
View file

@ -1,6 +1,7 @@
#include "jemalloc/internal/jemalloc_preamble.h"
#include "jemalloc/internal/background_thread.h"
#include "jemalloc/internal/background_thread_inlines.h"
#include "jemalloc/internal/deferral.h"
#include "jemalloc/internal/hpa.h"
#include "jemalloc/internal/pa.h"
@ -90,15 +91,21 @@ pa_shard_disable_hpa(tsdn_t *tsdn, pa_shard_t *shard) {
void
pa_shard_reset(tsdn_t *tsdn, pa_shard_t *shard) {
atomic_store_zu(&shard->nactive, 0, ATOMIC_RELAXED);
pa_shard_flush(tsdn, shard);
pa_shard_flush(tsdn, shard, /* all */ false);
}
void
pa_shard_flush(tsdn_t *tsdn, pa_shard_t *shard) {
pa_shard_flush(tsdn_t *tsdn, pa_shard_t *shard, bool all) {
pac_sec_flush(tsdn, &shard->pac);
if (shard->ever_used_hpa) {
hpa_shard_flush(tsdn, &shard->hpa);
}
if (all) {
pac_decay_all_now(tsdn, &shard->pac, extent_state_dirty);
if (pac_should_decay_muzzy(&shard->pac)) {
pac_decay_all_now(tsdn, &shard->pac, extent_state_muzzy);
}
}
}
static bool
@ -232,8 +239,8 @@ pa_dalloc(tsdn_t *tsdn, pa_shard_t *shard, edata_t *edata,
bool
pa_decay_ms_set(tsdn_t *tsdn, pa_shard_t *shard, extent_state_t state,
ssize_t decay_ms, pac_purge_eagerness_t eagerness) {
return pac_decay_ms_set(tsdn, &shard->pac, state, decay_ms, eagerness);
ssize_t decay_ms) {
return pac_decay_ms_set(tsdn, &shard->pac, state, decay_ms);
}
ssize_t
@ -250,17 +257,29 @@ pa_shard_set_deferral_allowed(
}
}
void
pa_shard_handle_deferred_work(tsdn_t *tsdn, pa_shard_t *shard) {
witness_assert_depth_to_rank(
tsdn_witness_tsdp_get(tsdn), WITNESS_RANK_CORE, 0);
if (pac_decay_immediately(&shard->pac)) {
pac_decay_all_now(tsdn, &shard->pac, extent_state_dirty);
}
if (background_thread_enabled()) {
pac_wake_bg_on_deferred(tsdn, &shard->pac);
}
}
void
pa_shard_do_deferred_work(
tsdn_t *tsdn, pa_shard_t *shard, pac_purge_eagerness_t eagerness) {
tsdn_t *tsdn, pa_shard_t *shard, bool is_background_thread) {
pac_do_deferred_work(tsdn, &shard->pac, is_background_thread);
/*
* The PAC result is only consumed on the application notification path,
* which calls pac_do_deferred_work directly. This facade just drives the
* work, so the result stays local.
* Application threads self-throttle HPA deferred work inline from their
* own alloc/dalloc path (hpa_shard_maybe_do_deferred_work, capped), so
* only drive it (forced, uncapped) from here on the background thread.
*/
pac_deferred_work_result_t result;
pac_do_deferred_work(tsdn, &shard->pac, eagerness, &result);
if (pa_shard_uses_hpa(shard)) {
if (is_background_thread && pa_shard_uses_hpa(shard)) {
hpa_shard_do_deferred_work(tsdn, &shard->hpa);
}
}

180
src/pac.c
View file

@ -2,6 +2,7 @@
#include "jemalloc/internal/arena.h"
#include "jemalloc/internal/background_thread.h"
#include "jemalloc/internal/background_thread_inlines.h"
#include "jemalloc/internal/deferral.h"
#include "jemalloc/internal/extent.h"
#include "jemalloc/internal/pac.h"
@ -807,8 +808,14 @@ pac_decay_deferred_one(tsdn_t *tsdn, pac_t *pac, decay_t *decay,
return epoch_advanced;
}
void
pac_do_deferred_work(tsdn_t *tsdn, pac_t *pac,
/*
* Non-forced deferred decay-purge for both the dirty and muzzy states, at the
* given eagerness; corresponding decay->mtx are acquired internally. Reports
* per-state epoch-advance in *result. JET_EXTERN: exposed for deterministic
* unit testing only; production callers use pac_do_deferred_work.
*/
JET_EXTERN void
pac_decay_deferred(tsdn_t *tsdn, pac_t *pac,
pac_purge_eagerness_t eagerness, pac_deferred_work_result_t *result) {
memset(result, 0, sizeof(*result));
@ -829,6 +836,151 @@ pac_do_deferred_work(tsdn_t *tsdn, pac_t *pac,
eagerness, &contended, &result->muzzy_npages_new);
}
/*
* This is the single, deliberate place where PAC reaches jointly into both a
* decay_t and a background_thread_info_t. It is intentionally NOT decoupled
* further, for two reasons:
* (a) The early-wake decision is intrinsically a JOINT info+decay
* computation: holding info->mtx (outer) we trylock decay->mtx (inner)
* to read remaining_sleep = wakeup_time - decay->epoch and the
* decay_npages_purge_in() estimate atomically against epoch advance.
* Splitting it would require copying these values across a new API while
* still holding both locks, adding interface surface for no behavioral
* gain.
* (b) It runs on the application FREE path (pac_do_deferred_work ->
* pac_maybe_wake_bg), where perf parity matters most.
*
* The info->mtx-outer / decay->mtx-inner trylock nesting is load-bearing for
* lock ordering; keep it.
*
* Parity trap: when npages_new == 0 (e.g. an epoch advanced with no new
* backlog) the accumulation below is skipped, but the THRESHOLD compare on the
* EXISTING info->npages_to_purge_new backlog still runs and can still trigger
* an early wakeup. Do not "simplify" by early-returning when npages_new == 0.
*/
static bool
pac_decay_should_wake_early(tsdn_t *tsdn, decay_t *decay,
background_thread_info_t *info, nstime_t *remaining_sleep,
size_t npages_new) {
malloc_mutex_assert_owner(tsdn, &info->mtx);
if (malloc_mutex_trylock(tsdn, &decay->mtx)) {
return false;
}
if (!decay_gradually(decay)) {
malloc_mutex_unlock(tsdn, &decay->mtx);
return false;
}
nstime_init(remaining_sleep, background_thread_wakeup_time_get(info));
if (nstime_compare(remaining_sleep, &decay->epoch) <= 0) {
malloc_mutex_unlock(tsdn, &decay->mtx);
return false;
}
nstime_subtract(remaining_sleep, &decay->epoch);
if (npages_new > 0) {
uint64_t npurge_new = decay_npages_purge_in(
decay, remaining_sleep, npages_new);
info->npages_to_purge_new += npurge_new;
}
malloc_mutex_unlock(tsdn, &decay->mtx);
return info->npages_to_purge_new
> PAC_DECAY_PURGE_NPAGES_THRESHOLD;
}
/*
* The PAC's base index is, under the current PA/PAC construction contract, the
* owning arena index (pa_shard_init asserts base_ind_get(base) == ind). This
* is a current construction invariant, not a permanent PAC guarantee.
*/
static unsigned
pac_ind_get(const pac_t *pac) {
return base_ind_get(pac->base);
}
/*
* Notify the background thread that a decay epoch advanced: if it sleeps
* indefinitely, wake it now; otherwise wake it early when the projected backlog
* crosses the purge threshold before its next scheduled wakeup. Non-blocking
* (trylocks info->mtx) to keep the application free path cheap.
*/
static void
pac_maybe_wake_bg(tsdn_t *tsdn, pac_t *pac, decay_t *decay, size_t npages_new) {
background_thread_info_t *info =
background_thread_info_get(pac_ind_get(pac));
if (malloc_mutex_trylock(tsdn, &info->mtx)) {
/*
* The background thread may hold the mutex for a while; keep this
* non-blocking and leave the work to a future epoch.
*/
return;
}
if (!background_thread_is_started(info)) {
goto label_done;
}
nstime_t remaining_sleep;
if (background_thread_indefinite_sleep(info)) {
background_thread_wakeup_early(info, NULL);
} else if (pac_decay_should_wake_early(tsdn, decay, info,
&remaining_sleep, npages_new)) {
info->npages_to_purge_new = 0;
background_thread_wakeup_early(info, &remaining_sleep);
}
label_done:
malloc_mutex_unlock(tsdn, &info->mtx);
}
/*
* A hook prepared for calling in pa: after a deferred work generated, wake the
* background thread only when it looks idle (lock-free acquire read of
* indefinite_sleep), then run the full early-wake decision under info->mtx.
*/
void
pac_wake_bg_on_deferred(tsdn_t *tsdn, pac_t *pac) {
background_thread_info_t *info =
background_thread_info_get(pac_ind_get(pac));
if (background_thread_indefinite_sleep(info)) {
pac_maybe_wake_bg(
tsdn, pac, &pac->decay_dirty, /* npages_new */ 0);
}
}
static pac_purge_eagerness_t pac_decide_purge_eagerness(
bool is_background_thread);
void
pac_do_deferred_work(tsdn_t *tsdn, pac_t *pac, bool is_background_thread) {
/*
* A concurrent background_thread enable/disable (mallctl) can race this
* path: the enable state is read lock-free twice below (for the eagerness
* decision, then the notify guard), so the two reads may disagree. Worst
* case is benign and self-healing:
* disabled->enabled: purged immediately, plus a possibly-redundant wake;
* enabled->disabled: deferred but not notified this pass -- the pages
* stay in the decay backlog and are reclaimed on the next decay tick or
* by the bg thread before it stops.
* It stays safe regardless: info is allocated once and never freed; the
* wake is gated by info->mtx + background_thread_is_started(); the bg-thread
* locks here are trylocks; and the purge runs under decay->mtx, which the
* toggle never touches.
*/
pac_purge_eagerness_t eagerness =
pac_decide_purge_eagerness(is_background_thread);
pac_deferred_work_result_t result;
pac_decay_deferred(tsdn, pac, eagerness, &result);
if (have_background_thread && background_thread_enabled()
&& !is_background_thread) {
if (result.dirty_epoch_advanced) {
pac_maybe_wake_bg(tsdn, pac, &pac->decay_dirty,
result.dirty_npages_new);
}
if (result.muzzy_epoch_advanced) {
pac_maybe_wake_bg(tsdn, pac, &pac->decay_muzzy,
result.muzzy_npages_new);
}
}
}
void
pac_decay_all_now(tsdn_t *tsdn, pac_t *pac, extent_state_t state) {
decay_t *decay;
@ -842,9 +994,25 @@ pac_decay_all_now(tsdn_t *tsdn, pac_t *pac, extent_state_t state) {
malloc_mutex_unlock(tsdn, &decay->mtx);
}
/*
* Decide the unforced decay-purge eagerness. On the background thread, force
* the purge; on an application thread, defer to the background thread when it is
* enabled, otherwise purge on the current thread on epoch advance.
*/
static pac_purge_eagerness_t
pac_decide_purge_eagerness(bool is_background_thread) {
if (is_background_thread) {
return PAC_PURGE_ALWAYS;
} else if (background_thread_enabled()) {
return PAC_PURGE_NEVER;
} else {
return PAC_PURGE_ON_EPOCH_ADVANCE;
}
}
bool
pac_decay_ms_set(tsdn_t *tsdn, pac_t *pac, extent_state_t state,
ssize_t decay_ms, pac_purge_eagerness_t eagerness) {
ssize_t decay_ms) {
decay_t *decay;
pac_decay_stats_t *decay_stats;
ecache_t *ecache;
@ -873,6 +1041,12 @@ pac_decay_ms_set(tsdn_t *tsdn, pac_t *pac, extent_state_t state,
nstime_t cur_time;
nstime_init_update(&cur_time);
decay_reinit(decay, &cur_time, decay_ms);
/*
* decay_ms is only ever set from a non-background thread (mallctl or
* arena init), so decide the eagerness here rather than threading it in.
*/
pac_purge_eagerness_t eagerness =
pac_decide_purge_eagerness(/* is_background_thread */ false);
pac_maybe_decay_purge(tsdn, pac, decay, decay_stats, ecache, eagerness);
malloc_mutex_unlock(tsdn, &decay->mtx);