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oomd: don't get pressure candidates on every interval

Only start collecting candidates for a memory pressure kill when we're
hitting the limit (but before the duration hitting that limit is
exceeded). This brings CPU util from ~1% to 0.3%.

Addresses CPU util from
https://bugzilla.redhat.com/show_bug.cgi?id=1941340
and
https://bugzilla.redhat.com/show_bug.cgi?id=1944646
This commit is contained in:
Anita Zhang 2021-03-26 01:53:15 -07:00
parent a858355e4a
commit cb13961ada

View File

@ -374,8 +374,17 @@ static int monitor_swap_contexts_handler(sd_event_source *s, uint64_t usec, void
return 0;
}
static void clear_candidate_hashmapp(Manager **m) {
if (*m)
hashmap_clear((*m)->monitored_mem_pressure_cgroup_contexts_candidates);
}
static int monitor_memory_pressure_contexts_handler(sd_event_source *s, uint64_t usec, void *userdata) {
/* Don't want to use stale candidate data. Setting this will clear the candidate hashmap on return unless we
* update the candidate data (in which case clear_candidates will be NULL). */
_cleanup_(clear_candidate_hashmapp) Manager *clear_candidates = userdata;
_cleanup_set_free_ Set *targets = NULL;
bool in_post_action_delay = false;
Manager *m = userdata;
usec_t usec_now;
int r;
@ -400,10 +409,8 @@ static int monitor_memory_pressure_contexts_handler(sd_event_source *s, uint64_t
}
/* Return early if nothing is requesting memory pressure monitoring */
if (hashmap_isempty(m->monitored_mem_pressure_cgroup_contexts)) {
hashmap_clear(m->monitored_mem_pressure_cgroup_contexts_candidates);
if (hashmap_isempty(m->monitored_mem_pressure_cgroup_contexts))
return 0;
}
/* Update the cgroups used for detection/action */
r = update_monitored_cgroup_contexts(&m->monitored_mem_pressure_cgroup_contexts);
@ -423,7 +430,7 @@ static int monitor_memory_pressure_contexts_handler(sd_event_source *s, uint64_t
* values and go on a kill storm. */
if (m->mem_pressure_post_action_delay_start > 0) {
if (m->mem_pressure_post_action_delay_start + POST_ACTION_DELAY_USEC > usec_now)
return 0;
in_post_action_delay = true;
else
m->mem_pressure_post_action_delay_start = 0;
}
@ -433,7 +440,7 @@ static int monitor_memory_pressure_contexts_handler(sd_event_source *s, uint64_t
return log_oom();
if (r < 0)
log_debug_errno(r, "Failed to check if memory pressure exceeded limits, ignoring: %m");
else if (r == 1) {
else if (r == 1 && !in_post_action_delay) {
OomdCGroupContext *t;
SET_FOREACH(t, targets) {
_cleanup_free_ char *selected = NULL;
@ -455,6 +462,15 @@ static int monitor_memory_pressure_contexts_handler(sd_event_source *s, uint64_t
m->default_mem_pressure_duration_usec,
USEC_PER_SEC));
r = update_monitored_cgroup_contexts_candidates(
m->monitored_mem_pressure_cgroup_contexts, &m->monitored_mem_pressure_cgroup_contexts_candidates);
if (r == -ENOMEM)
return log_oom();
if (r < 0)
log_debug_errno(r, "Failed to update monitored memory pressure candidate cgroup contexts, ignoring: %m");
else
clear_candidates = NULL;
r = oomd_kill_by_pgscan_rate(m->monitored_mem_pressure_cgroup_contexts_candidates, t->path, m->dry_run, &selected);
if (r == -ENOMEM)
return log_oom();
@ -475,6 +491,28 @@ static int monitor_memory_pressure_contexts_handler(sd_event_source *s, uint64_t
return 0;
}
}
} else {
/* If any monitored cgroup is over their pressure limit, get all the kill candidates for every
* monitored cgroup. This saves CPU cycles from doing it every interval by only doing it when a kill
* might happen.
* Candidate cgroup data will continue to get updated during the post-action delay period in case
* pressure continues to be high after a kill. */
OomdCGroupContext *c;
HASHMAP_FOREACH(c, m->monitored_mem_pressure_cgroup_contexts) {
if (c->mem_pressure_limit_hit_start == 0)
continue;
r = update_monitored_cgroup_contexts_candidates(
m->monitored_mem_pressure_cgroup_contexts, &m->monitored_mem_pressure_cgroup_contexts_candidates);
if (r == -ENOMEM)
return log_oom();
if (r < 0)
log_debug_errno(r, "Failed to update monitored memory pressure candidate cgroup contexts, ignoring: %m");
else {
clear_candidates = NULL;
break;
}
}
}
return 0;