cgroup_pids: don't account for the root cgroup (67cde9c4) · Commits · 戴 / test

Because accounting resources for the root cgroup sometimes incurs measureable overhead for workloads which don't care about cgroup and often ends up calculating a number which is available elsewhere in a slightly different form, cgroup is not in the business of providing system-wide statistics. The pids controller which was introduced recently was exposing "pids.current" at the root. This patch disable accounting for root cgroup and removes the file from the root directory. While this is a userland visible behavior change, pids has been available only in one version and was badly broken there, so I don't think this will be noticeable. If it turns out to be a problem, we can reinstate it for v1 hierarchies. Signed-off-by:

Tejun Heo <tj@kernel.org> Cc: Aleksa Sarai <cyphar@cyphar.com>

kernel/cgroup_pids.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -106,7 +106,7 @@ static void pids_uncharge(struct pids_cgroup *pids, int num)
		{
		struct pids_cgroup *p;

		for (p = pids; p; p = parent_pids(p))
		for (p = pids; parent_pids(p); p = parent_pids(p))
		pids_cancel(p, num);
		}

		@@ -123,7 +123,7 @@ static void pids_charge(struct pids_cgroup *pids, int num)
		{
		struct pids_cgroup *p;

		for (p = pids; p; p = parent_pids(p))
		for (p = pids; parent_pids(p); p = parent_pids(p))
		atomic64_add(num, &p->counter);
		}

		@@ -140,7 +140,7 @@ static int pids_try_charge(struct pids_cgroup *pids, int num)
		{
		struct pids_cgroup p, q;

		for (p = pids; p; p = parent_pids(p)) {
		for (p = pids; parent_pids(p); p = parent_pids(p)) {
		int64_t new = atomic64_add_return(num, &p->counter);

		/*
		@@ -298,6 +298,7 @@ static struct cftype pids_files[] = {
		{
		.name = "current",
		.read_s64 = pids_current_read,
		.flags = CFTYPE_NOT_ON_ROOT,
		},
		{ } /* terminate */
		};

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