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Clean up background thread sleep computation

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Isolate the computation of purge interval from background thread logic and
move into more suitable file.
This commit is contained in:
Alex Lapenkou 2021-07-16 14:53:25 -07:00 committed by Qi Wang
parent 6630c59896
commit 4b633b9a81
3 changed files with 133 additions and 130 deletions
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11
include/jemalloc/internal/decay.h
View File

@ -3,6 +3,8 @@
#include "jemalloc/internal/smoothstep.h"
#define DECAY_UNBOUNDED_TIME_TO_PURGE ((uint64_t)-1)
/*
* The decay_t computes the number of pages we should purge at any given time.
* Page allocators inform a decay object when pages enter a decay-able state
@ -146,4 +148,13 @@ void decay_reinit(decay_t *decay, nstime_t *cur_time, ssize_t decay_ms);
bool decay_maybe_advance_epoch(decay_t *decay, nstime_t *new_time,
size_t current_npages);
/*
* Calculates wait time until at least npages_threshold pages should be purged.
*
* Returns number of nanoseconds or DECAY_UNBOUNDED_TIME_TO_PURGE in case of
* indefinite wait.
*/
uint64_t decay_ns_until_purge(decay_t *decay, size_t npages_current,
uint64_t npages_threshold);
#endif /* JEMALLOC_INTERNAL_DECAY_H */

179
src/background_thread.c
View File

@ -104,134 +104,6 @@ set_current_thread_affinity(int cpu) {
/* Minimal sleep interval 100 ms. */
#define BACKGROUND_THREAD_MIN_INTERVAL_NS (BILLION / 10)
static inline size_t
decay_npurge_after_interval(decay_t *decay, size_t interval) {
size_t i;
uint64_t sum = 0;
for (i = 0; i < interval; i++) {
sum += decay->backlog[i] * h_steps[i];
}
for (; i < SMOOTHSTEP_NSTEPS; i++) {
sum += decay->backlog[i] * (h_steps[i] - h_steps[i - interval]);
}
return (size_t)(sum >> SMOOTHSTEP_BFP);
}
static uint64_t
arena_decay_compute_purge_interval_impl(tsdn_t *tsdn, decay_t *decay,
ecache_t *ecache) {
if (malloc_mutex_trylock(tsdn, &decay->mtx)) {
/* Use minimal interval if decay is contended. */
return BACKGROUND_THREAD_MIN_INTERVAL_NS;
}
uint64_t interval;
ssize_t decay_time = decay_ms_read(decay);
if (decay_time <= 0) {
/* Purging is eagerly done or disabled currently. */
interval = BACKGROUND_THREAD_INDEFINITE_SLEEP;
goto label_done;
}
uint64_t decay_interval_ns = decay_epoch_duration_ns(decay);
assert(decay_interval_ns > 0);
size_t npages = ecache_npages_get(ecache);
if (npages == 0) {
unsigned i;
for (i = 0; i < SMOOTHSTEP_NSTEPS; i++) {
if (decay->backlog[i] > 0) {
break;
}
}
if (i == SMOOTHSTEP_NSTEPS) {
/* No dirty pages recorded. Sleep indefinitely. */
interval = BACKGROUND_THREAD_INDEFINITE_SLEEP;
goto label_done;
}
}
if (npages <= BACKGROUND_THREAD_NPAGES_THRESHOLD) {
/* Use max interval. */
interval = decay_interval_ns * SMOOTHSTEP_NSTEPS;
goto label_done;
}
size_t lb = BACKGROUND_THREAD_MIN_INTERVAL_NS / decay_interval_ns;
size_t ub = SMOOTHSTEP_NSTEPS;
/* Minimal 2 intervals to ensure reaching next epoch deadline. */
lb = (lb < 2) ? 2 : lb;
if ((decay_interval_ns * ub <= BACKGROUND_THREAD_MIN_INTERVAL_NS) ||
(lb + 2 > ub)) {
interval = BACKGROUND_THREAD_MIN_INTERVAL_NS;
goto label_done;
}
assert(lb + 2 <= ub);
size_t npurge_lb, npurge_ub;
npurge_lb = decay_npurge_after_interval(decay, lb);
if (npurge_lb > BACKGROUND_THREAD_NPAGES_THRESHOLD) {
interval = decay_interval_ns * lb;
goto label_done;
}
npurge_ub = decay_npurge_after_interval(decay, ub);
if (npurge_ub < BACKGROUND_THREAD_NPAGES_THRESHOLD) {
interval = decay_interval_ns * ub;
goto label_done;
}
unsigned n_search = 0;
size_t target, npurge;
while ((npurge_lb + BACKGROUND_THREAD_NPAGES_THRESHOLD < npurge_ub)
&& (lb + 2 < ub)) {
target = (lb + ub) / 2;
npurge = decay_npurge_after_interval(decay, target);
if (npurge > BACKGROUND_THREAD_NPAGES_THRESHOLD) {
ub = target;
npurge_ub = npurge;
} else {
lb = target;
npurge_lb = npurge;
}
assert(n_search < lg_floor(SMOOTHSTEP_NSTEPS) + 1);
++n_search;
}
interval = decay_interval_ns * (ub + lb) / 2;
label_done:
interval = (interval < BACKGROUND_THREAD_MIN_INTERVAL_NS) ?
BACKGROUND_THREAD_MIN_INTERVAL_NS : interval;
malloc_mutex_unlock(tsdn, &decay->mtx);
return interval;
}
/* Compute purge interval for background threads. */
static uint64_t
arena_decay_compute_purge_interval(tsdn_t *tsdn, arena_t *arena) {
uint64_t i1, i2;
i1 = arena_decay_compute_purge_interval_impl(tsdn,
&arena->pa_shard.pac.decay_dirty, &arena->pa_shard.pac.ecache_dirty);
if (i1 == BACKGROUND_THREAD_MIN_INTERVAL_NS) {
return i1;
}
i2 = arena_decay_compute_purge_interval_impl(tsdn,
&arena->pa_shard.pac.decay_muzzy, &arena->pa_shard.pac.ecache_muzzy);
uint64_t min_so_far = i1 < i2 ? i1 : i2;
if (opt_background_thread_hpa_interval_max_ms >= 0) {
uint64_t hpa_interval = 1000 * 1000 *
(uint64_t)opt_background_thread_hpa_interval_max_ms;
if (hpa_interval < min_so_far) {
if (hpa_interval < BACKGROUND_THREAD_MIN_INTERVAL_NS) {
min_so_far = BACKGROUND_THREAD_MIN_INTERVAL_NS;
} else {
min_so_far = hpa_interval;
}
}
}
return min_so_far;
}
static void
background_thread_sleep(tsdn_t *tsdn, background_thread_info_t *info,
uint64_t interval) {
@ -301,6 +173,52 @@ background_thread_pause_check(tsdn_t *tsdn, background_thread_info_t *info) {
return false;
}
static inline uint64_t
arena_decay_compute_purge_interval(tsdn_t *tsdn, decay_t *decay,
size_t npages) {
if (malloc_mutex_trylock(tsdn, &decay->mtx)) {
/* Use minimal interval if decay is contended. */
return BACKGROUND_THREAD_MIN_INTERVAL_NS;
}
uint64_t decay_ns = decay_ns_until_purge(decay, npages,
BACKGROUND_THREAD_NPAGES_THRESHOLD);
malloc_mutex_unlock(tsdn, &decay->mtx);
return decay_ns < BACKGROUND_THREAD_MIN_INTERVAL_NS ?
BACKGROUND_THREAD_MIN_INTERVAL_NS :
decay_ns;
}
static inline uint64_t
arena_decay_compute_min_purge_interval(tsdn_t *tsdn, arena_t *arena) {
uint64_t dirty, muzzy;
dirty = arena_decay_compute_purge_interval(tsdn,
&arena->pa_shard.pac.decay_dirty,
ecache_npages_get(&arena->pa_shard.pac.ecache_dirty));
if (dirty == BACKGROUND_THREAD_MIN_INTERVAL_NS) {
return dirty;
}
muzzy = arena_decay_compute_purge_interval(tsdn,
&arena->pa_shard.pac.decay_muzzy,
ecache_npages_get(&arena->pa_shard.pac.ecache_muzzy));
uint64_t min_so_far = dirty < muzzy ? dirty : muzzy;
if (opt_background_thread_hpa_interval_max_ms >= 0) {
uint64_t hpa_interval = 1000 * 1000 *
(uint64_t)opt_background_thread_hpa_interval_max_ms;
if (hpa_interval < min_so_far) {
if (hpa_interval < BACKGROUND_THREAD_MIN_INTERVAL_NS) {
min_so_far = BACKGROUND_THREAD_MIN_INTERVAL_NS;
} else {
min_so_far = hpa_interval;
}
}
}
return min_so_far;
}
static inline void
background_work_sleep_once(tsdn_t *tsdn, background_thread_info_t *info, unsigned ind) {
uint64_t min_interval = BACKGROUND_THREAD_INDEFINITE_SLEEP;
@ -316,10 +234,11 @@ background_work_sleep_once(tsdn_t *tsdn, background_thread_info_t *info, unsigne
/* Min interval will be used. */
continue;
}
uint64_t interval = arena_decay_compute_purge_interval(tsdn,
uint64_t interval = arena_decay_compute_min_purge_interval(tsdn,
arena);
assert(interval >= BACKGROUND_THREAD_MIN_INTERVAL_NS);
if (min_interval > interval) {
if (interval != DECAY_UNBOUNDED_TIME_TO_PURGE &&
min_interval > interval) {
min_interval = interval;
}
}

73
src/decay.c
View File

@ -175,3 +175,76 @@ decay_maybe_advance_epoch(decay_t *decay, nstime_t *new_time,
return true;
}
static inline size_t
decay_npurge_after_interval(decay_t *decay, size_t interval) {
size_t i;
uint64_t sum = 0;
for (i = 0; i < interval; i++) {
sum += decay->backlog[i] * h_steps[i];
}
for (; i < SMOOTHSTEP_NSTEPS; i++) {
sum += decay->backlog[i] *
(h_steps[i] - h_steps[i - interval]);
}
return (size_t)(sum >> SMOOTHSTEP_BFP);
}
uint64_t decay_ns_until_purge(decay_t *decay, size_t npages_current,
uint64_t npages_threshold) {
ssize_t decay_time = decay_ms_read(decay);
if (decay_time <= 0) {
/* Purging is eagerly done or disabled currently. */
return DECAY_UNBOUNDED_TIME_TO_PURGE;
}
uint64_t decay_interval_ns = decay_epoch_duration_ns(decay);
assert(decay_interval_ns > 0);
if (npages_current == 0) {
unsigned i;
for (i = 0; i < SMOOTHSTEP_NSTEPS; i++) {
if (decay->backlog[i] > 0) {
break;
}
}
if (i == SMOOTHSTEP_NSTEPS) {
/* No dirty pages recorded. Sleep indefinitely. */
return DECAY_UNBOUNDED_TIME_TO_PURGE;
}
}
if (npages_current <= npages_threshold) {
/* Use max interval. */
return decay_interval_ns * SMOOTHSTEP_NSTEPS;
}
/* Minimal 2 intervals to ensure reaching next epoch deadline. */
size_t lb = 2;
size_t ub = SMOOTHSTEP_NSTEPS;
size_t npurge_lb, npurge_ub;
npurge_lb = decay_npurge_after_interval(decay, lb);
if (npurge_lb > npages_threshold) {
return decay_interval_ns * lb;
}
npurge_ub = decay_npurge_after_interval(decay, ub);
if (npurge_ub < npages_threshold) {
return decay_interval_ns * ub;
}
unsigned n_search = 0;
size_t target, npurge;
while ((npurge_lb + npages_threshold < npurge_ub) && (lb + 2 < ub)) {
target = (lb + ub) / 2;
npurge = decay_npurge_after_interval(decay, target);
if (npurge > npages_threshold) {
ub = target;
npurge_ub = npurge;
} else {
lb = target;
npurge_lb = npurge;
}
assert(n_search < lg_floor(SMOOTHSTEP_NSTEPS) + 1);
++n_search;
}
return decay_interval_ns * (ub + lb) / 2;
}