diff options
| author | Josh Don <joshdon@google.com> | 2022-08-31 15:49:03 -0700 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2022-09-04 09:26:51 -1000 |
| commit | 5251c6c436edf81e5f27de31ca34bcdc12fc94e1 (patch) | |
| tree | 8bc0c6ccbd7ec56530f1779063716b729fd83534 /kernel/cgroup | |
| parent | dc79ec1b232ad2c165d381d3dd2626df4ef9b5a4 (diff) | |
cgroup: add pids.peak interface for pids controller
pids.peak tracks the high watermark of usage for number of pids. This
helps give a better baseline on which to set pids.max. Polling
pids.current isn't really feasible, since it would potentially miss
short-lived spikes.
This interface is analogous to memory.peak.
Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup')
| -rw-r--r-- | kernel/cgroup/pids.c | 37 |
1 files changed, 35 insertions, 2 deletions
diff --git a/kernel/cgroup/pids.c b/kernel/cgroup/pids.c index 511af87f685e..7695e60bcb40 100644 --- a/kernel/cgroup/pids.c +++ b/kernel/cgroup/pids.c @@ -47,6 +47,7 @@ struct pids_cgroup { */ atomic64_t counter; atomic64_t limit; + int64_t watermark; /* Handle for "pids.events" */ struct cgroup_file events_file; @@ -85,6 +86,16 @@ static void pids_css_free(struct cgroup_subsys_state *css) kfree(css_pids(css)); } +static void pids_update_watermark(struct pids_cgroup *p, int64_t nr_pids) +{ + /* + * This is racy, but we don't need perfectly accurate tallying of + * the watermark, and this lets us avoid extra atomic overhead. + */ + if (nr_pids > READ_ONCE(p->watermark)) + WRITE_ONCE(p->watermark, nr_pids); +} + /** * pids_cancel - uncharge the local pid count * @pids: the pid cgroup state @@ -128,8 +139,11 @@ static void pids_charge(struct pids_cgroup *pids, int num) { struct pids_cgroup *p; - for (p = pids; parent_pids(p); p = parent_pids(p)) - atomic64_add(num, &p->counter); + for (p = pids; parent_pids(p); p = parent_pids(p)) { + int64_t new = atomic64_add_return(num, &p->counter); + + pids_update_watermark(p, new); + } } /** @@ -156,6 +170,12 @@ static int pids_try_charge(struct pids_cgroup *pids, int num) */ if (new > limit) goto revert; + + /* + * Not technically accurate if we go over limit somewhere up + * the hierarchy, but that's tolerable for the watermark. + */ + pids_update_watermark(p, new); } return 0; @@ -311,6 +331,14 @@ static s64 pids_current_read(struct cgroup_subsys_state *css, return atomic64_read(&pids->counter); } +static s64 pids_peak_read(struct cgroup_subsys_state *css, + struct cftype *cft) +{ + struct pids_cgroup *pids = css_pids(css); + + return READ_ONCE(pids->watermark); +} + static int pids_events_show(struct seq_file *sf, void *v) { struct pids_cgroup *pids = css_pids(seq_css(sf)); @@ -332,6 +360,11 @@ static struct cftype pids_files[] = { .flags = CFTYPE_NOT_ON_ROOT, }, { + .name = "peak", + .flags = CFTYPE_NOT_ON_ROOT, + .read_s64 = pids_peak_read, + }, + { .name = "events", .seq_show = pids_events_show, .file_offset = offsetof(struct pids_cgroup, events_file), |