Skip to content

Use CLOCK_MONOTONIC for background thread sleep to prevent clock rollback stalls #4

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
antonio2368 merged 3 commits into from
Apr 2, 2026
Merged

Use CLOCK_MONOTONIC for background thread sleep to prevent clock rollback stalls #4

Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
86a24dd
Use monotonic clock for background thread sleep timing
antonio2368 Apr 1, 2026
f3365c8
Use nstime_init_update for sleep timing and handle condattr_setclock …
antonio2368 Apr 2, 2026
861db0b
Handle pthread_condattr_init failure in background thread
antonio2368 Apr 2, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
47 changes: 41 additions & 6 deletions src/background_thread.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -189,11 +189,8 @@ background_thread_sleep(
}
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);
nstime_init_update(&before_sleep);

int ret;
if (interval == BACKGROUND_THREAD_INDEFINITE_SLEEP) {
Expand Down Expand Up @@ -225,9 +222,8 @@ background_thread_sleep(
assert(ret == ETIMEDOUT || ret == 0);
}
if (config_stats) {
gettimeofday(&tv, NULL);
nstime_t after_sleep;
nstime_init2(&after_sleep, tv.tv_sec, tv.tv_usec * 1000);
nstime_init_update(&after_sleep);
if (nstime_compare(&after_sleep, &before_sleep) > 0) {
nstime_subtract(&after_sleep, &before_sleep);
nstime_add(&info->tot_sleep_time, &after_sleep);
Expand Down Expand Up @@ -741,7 +737,27 @@ background_thread_postfork_child(tsdn_t *tsdn) {
background_thread_info_t *info = &background_thread_info[i];
malloc_mutex_lock(tsdn, &info->mtx);
info->state = background_thread_stopped;
#if defined(JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE) || defined(JEMALLOC_HAVE_CLOCK_MONOTONIC)
int ret;
pthread_condattr_t cond_attr;
if (pthread_condattr_init(&cond_attr)) {
ret = pthread_cond_init(&info->cond, NULL);
} else if (pthread_condattr_setclock(&cond_attr,
CLOCK_MONOTONIC)) {
/*
* Fall back to default (CLOCK_REALTIME)
* attributes if setclock fails.
*/
pthread_condattr_destroy(&cond_attr);
ret = pthread_cond_init(&info->cond, NULL);
} else {
ret = pthread_cond_init(&info->cond,
&cond_attr);
pthread_condattr_destroy(&cond_attr);
}
#else
int ret = pthread_cond_init(&info->cond, NULL);
#endif
assert(ret == 0);
background_thread_info_init(tsdn, info);
malloc_mutex_unlock(tsdn, &info->mtx);
Expand Down Expand Up @@ -859,9 +875,28 @@ background_thread_boot1(tsdn_t *tsdn, base_t *base) {
malloc_mutex_address_ordered)) {
return true;
}
#if defined(JEMALLOC_HAVE_CLOCK_MONOTONIC_COARSE) || defined(JEMALLOC_HAVE_CLOCK_MONOTONIC)
{
pthread_condattr_t cond_attr;
if (pthread_condattr_init(&cond_attr)) {
return true;
}
if (pthread_condattr_setclock(&cond_attr,
CLOCK_MONOTONIC)) {
pthread_condattr_destroy(&cond_attr);
return true;
}
if (pthread_cond_init(&info->cond, &cond_attr)) {
pthread_condattr_destroy(&cond_attr);
return true;
}
pthread_condattr_destroy(&cond_attr);
}
#else
if (pthread_cond_init(&info->cond, NULL)) {
return true;
}
#endif
malloc_mutex_lock(tsdn, &info->mtx);
info->state = background_thread_stopped;
background_thread_info_init(tsdn, info);
Expand Down
Loading