Commit 5251c6c4 authored by Josh Don's avatar Josh Don Committed by Tejun Heo
Browse files

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: default avatarJosh Don <joshdon@google.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent dc79ec1b

kernel/cgroup/pids.c

+35 −2
Original line number Diff line number Diff line
@@ -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));
@@ -331,6 +359,11 @@ static struct cftype pids_files[] = { 
		.read_s64 = pids_current_read,

		.flags = CFTYPE_NOT_ON_ROOT,

	},

	{

		.name = "peak",

		.flags = CFTYPE_NOT_ON_ROOT,

		.read_s64 = pids_peak_read,

	},

	{

		.name = "events",

		.seq_show = pids_events_show,