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Check for background thread inactivity on extents_dalloc.

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To avoid background threads sleeping forever with idle arenas, we eagerly check
background threads' sleep time after extents_dalloc, and signal the thread if
necessary.
This commit is contained in:
Qi Wang 2017-05-22 15:26:25 -07:00 committed by Qi Wang
parent 2c368284d2
commit 0eae838b0d
4 changed files with 91 additions and 23 deletions
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35
include/jemalloc/internal/background_thread_inlines.h
View File

@ -18,4 +18,39 @@ arena_background_thread_info_get(arena_t *arena) {
return &background_thread_info[arena_ind % ncpus];
}
JEMALLOC_ALWAYS_INLINE uint64_t
background_thread_wakeup_time_get(background_thread_info_t *info) {
uint64_t next_wakeup = nstime_ns(&info->next_wakeup);
assert(atomic_load_b(&info->indefinite_sleep, ATOMIC_ACQUIRE) ==
(next_wakeup == BACKGROUND_THREAD_INDEFINITE_SLEEP));
return next_wakeup;
}
JEMALLOC_ALWAYS_INLINE void
background_thread_wakeup_time_set(tsdn_t *tsdn, background_thread_info_t *info,
uint64_t wakeup_time) {
malloc_mutex_assert_owner(tsdn, &info->mtx);
atomic_store_b(&info->indefinite_sleep,
wakeup_time == BACKGROUND_THREAD_INDEFINITE_SLEEP, ATOMIC_RELEASE);
nstime_init(&info->next_wakeup, wakeup_time);
}
JEMALLOC_ALWAYS_INLINE bool
background_thread_indefinite_sleep(background_thread_info_t *info) {
return atomic_load_b(&info->indefinite_sleep, ATOMIC_ACQUIRE);
}
JEMALLOC_ALWAYS_INLINE void
arena_background_thread_inactivity_check(tsdn_t *tsdn, arena_t *arena) {
if (!background_thread_enabled()) {
return;
}
background_thread_info_t *info =
arena_background_thread_info_get(arena);
if (background_thread_indefinite_sleep(info)) {
background_thread_interval_check(tsdn, arena,
&arena->decay_dirty, 0);
}
}
#endif /* JEMALLOC_INTERNAL_BACKGROUND_THREAD_INLINES_H */

14
include/jemalloc/internal/background_thread_structs.h
View File

@ -1,15 +1,22 @@
#ifndef JEMALLOC_INTERNAL_BACKGROUND_THREAD_STRUCTS_H
#define JEMALLOC_INTERNAL_BACKGROUND_THREAD_STRUCTS_H
/* This file really combines "structs" and "types", but only transitionally. */
#define BACKGROUND_THREAD_INDEFINITE_SLEEP UINT64_MAX
struct background_thread_info_s {
malloc_mutex_t mtx;
#ifdef JEMALLOC_BACKGROUND_THREAD
/* Background thread is pthread specific. */
pthread_cond_t cond;
pthread_t thread;
pthread_cond_t cond;
#endif
malloc_mutex_t mtx;
/* Whether the thread has been created. */
bool started;
/* Next scheduled wakeup time (absolute time). */
/* When true, it means no wakeup scheduled. */
atomic_b_t indefinite_sleep;
/* Next scheduled wakeup time (absolute time in ns). */
nstime_t next_wakeup;
/*
* Since the last background thread run, newly added number of pages
@ -22,7 +29,6 @@ struct background_thread_info_s {
uint64_t tot_n_runs;
/* Stats: total sleep time since started. */
nstime_t tot_sleep_time;
#endif /* ifdef JEMALLOC_BACKGROUND_THREAD */
};
typedef struct background_thread_info_s background_thread_info_t;

4
src/arena.c
View File

@ -367,6 +367,8 @@ arena_extents_dirty_dalloc(tsdn_t *tsdn, arena_t *arena,
extent);
if (arena_dirty_decay_ms_get(arena) == 0) {
arena_decay_dirty(tsdn, arena, false, true);
} else {
arena_background_thread_inactivity_check(tsdn, arena);
}
}
@ -919,6 +921,8 @@ arena_decay_stashed(tsdn_t *tsdn, arena_t *arena,
extent_size_get(extent))) {
extents_dalloc(tsdn, arena, r_extent_hooks,
&arena->extents_muzzy, extent);
arena_background_thread_inactivity_check(tsdn,
arena);
break;
}
/* Fall through. */

61
src/background_thread.c
View File

@ -42,8 +42,8 @@ bool background_thread_stats_read(tsdn_t *tsdn,
#else
static void
background_thread_info_reinit(background_thread_info_t *info) {
nstime_init(&info->next_wakeup, 0);
background_thread_info_reinit(tsdn_t *tsdn, background_thread_info_t *info) {
background_thread_wakeup_time_set(tsdn, info, 0);
info->npages_to_purge_new = 0;
if (config_stats) {
info->tot_n_runs = 0;
@ -80,8 +80,10 @@ background_threads_init(tsd_t *tsd) {
if (pthread_cond_init(&info->cond, NULL)) {
return true;
}
malloc_mutex_lock(tsd_tsdn(tsd), &info->mtx);
info->started = false;
background_thread_info_reinit(info);
background_thread_info_reinit(tsd_tsdn(tsd), info);
malloc_mutex_unlock(tsd_tsdn(tsd), &info->mtx);
}
return false;
@ -106,7 +108,6 @@ set_current_thread_affinity(UNUSED int cpu) {
#define BILLION UINT64_C(1000000000)
/* Minimal sleep interval 100 ms. */
#define BACKGROUND_THREAD_MIN_INTERVAL_NS (BILLION / 10)
#define BACKGROUND_THREAD_INDEFINITE_SLEEP UINT64_MAX
static inline size_t
decay_npurge_after_interval(arena_decay_t *decay, size_t interval) {
@ -258,6 +259,8 @@ background_work(tsdn_t *tsdn, unsigned ind) {
background_thread_info_t *info = &background_thread_info[ind];
malloc_mutex_lock(tsdn, &info->mtx);
background_thread_wakeup_time_set(tsdn, info,
BACKGROUND_THREAD_INDEFINITE_SLEEP);
while (info->started) {
uint64_t interval = background_work_once(tsdn, ind);
if (config_stats) {
@ -266,21 +269,27 @@ background_work(tsdn_t *tsdn, unsigned ind) {
info->npages_to_purge_new = 0;
struct timeval tv;
/* Specific clock required by timedwait. */
gettimeofday(&tv, NULL);
nstime_t before_sleep;
nstime_init2(&before_sleep, tv.tv_sec, tv.tv_usec * 1000);
if (interval == BACKGROUND_THREAD_INDEFINITE_SLEEP) {
nstime_init(&info->next_wakeup,
BACKGROUND_THREAD_INDEFINITE_SLEEP);
assert(background_thread_indefinite_sleep(info));
ret = pthread_cond_wait(&info->cond, &info->mtx.lock);
assert(ret == 0);
} else {
assert(interval >= BACKGROUND_THREAD_MIN_INTERVAL_NS &&
interval <= BACKGROUND_THREAD_INDEFINITE_SLEEP);
nstime_init(&info->next_wakeup, 0);
nstime_update(&info->next_wakeup);
nstime_iadd(&info->next_wakeup, interval);
/* We need malloc clock (can be different from tv). */
nstime_t next_wakeup;
nstime_init(&next_wakeup, 0);
nstime_update(&next_wakeup);
nstime_iadd(&next_wakeup, interval);
assert(nstime_ns(&next_wakeup) <
BACKGROUND_THREAD_INDEFINITE_SLEEP);
background_thread_wakeup_time_set(tsdn, info,
nstime_ns(&next_wakeup));
nstime_t ts_wakeup;
nstime_copy(&ts_wakeup, &before_sleep);
@ -289,9 +298,12 @@ background_work(tsdn_t *tsdn, unsigned ind) {
ts.tv_sec = (size_t)nstime_sec(&ts_wakeup);
ts.tv_nsec = (size_t)nstime_nsec(&ts_wakeup);
assert(!background_thread_indefinite_sleep(info));
ret = pthread_cond_timedwait(&info->cond,
&info->mtx.lock, &ts);
assert(ret == ETIMEDOUT || ret == 0);
background_thread_wakeup_time_set(tsdn, info,
BACKGROUND_THREAD_INDEFINITE_SLEEP);
}
if (config_stats) {
@ -304,6 +316,7 @@ background_work(tsdn_t *tsdn, unsigned ind) {
}
}
}
background_thread_wakeup_time_set(tsdn, info, 0);
malloc_mutex_unlock(tsdn, &info->mtx);
}
@ -360,7 +373,7 @@ background_thread_create(tsd_t *tsd, unsigned arena_ind) {
assert(info->started == false);
if (err == 0) {
info->started = true;
background_thread_info_reinit(info);
background_thread_info_reinit(tsd_tsdn(tsd), info);
n_background_threads++;
}
malloc_mutex_unlock(tsd_tsdn(tsd), &info->mtx);
@ -465,6 +478,7 @@ background_thread_interval_check(tsdn_t *tsdn, arena_t *arena,
if (!info->started) {
goto label_done;
}
assert(background_thread_enabled());
if (malloc_mutex_trylock(tsdn, &decay->mtx)) {
goto label_done;
}
@ -474,14 +488,14 @@ background_thread_interval_check(tsdn_t *tsdn, arena_t *arena,
/* Purging is eagerly done or disabled currently. */
goto label_done_unlock2;
}
if (nstime_compare(&info->next_wakeup, &decay->epoch) <= 0) {
goto label_done_unlock2;
}
uint64_t decay_interval_ns = nstime_ns(&decay->interval);
assert(decay_interval_ns > 0);
nstime_t diff;
nstime_copy(&diff, &info->next_wakeup);
nstime_init(&diff, background_thread_wakeup_time_get(info));
if (nstime_compare(&diff, &decay->epoch) <= 0) {
goto label_done_unlock2;
}
nstime_subtract(&diff, &decay->epoch);
if (nstime_ns(&diff) < BACKGROUND_THREAD_MIN_INTERVAL_NS) {
goto label_done_unlock2;
@ -508,9 +522,19 @@ background_thread_interval_check(tsdn_t *tsdn, arena_t *arena,
info->npages_to_purge_new += npurge_new;
}
if (info->npages_to_purge_new > BACKGROUND_THREAD_NPAGES_THRESHOLD ||
(nstime_ns(&info->next_wakeup) ==
BACKGROUND_THREAD_INDEFINITE_SLEEP && info->npages_to_purge_new > 0)) {
bool should_signal;
if (info->npages_to_purge_new > BACKGROUND_THREAD_NPAGES_THRESHOLD) {
should_signal = true;
} else if (unlikely(background_thread_indefinite_sleep(info)) &&
(extents_npages_get(&arena->extents_dirty) > 0 ||
extents_npages_get(&arena->extents_muzzy) > 0 ||
info->npages_to_purge_new > 0)) {
should_signal = true;
} else {
should_signal = false;
}
if (should_signal) {
info->npages_to_purge_new = 0;
pthread_cond_signal(&info->cond);
}
@ -602,7 +626,6 @@ background_thread_stats_read(tsdn_t *tsdn, background_thread_stats_t *stats) {
#undef BACKGROUND_THREAD_NPAGES_THRESHOLD
#undef BILLION
#undef BACKGROUND_THREAD_MIN_INTERVAL_NS
#undef BACKGROUND_THREAD_INDEFINITE_SLEEP
#endif /* defined(JEMALLOC_BACKGROUND_THREAD) */