Commit 8e20d4b3 authored by Ganesan Rajagopal's avatar Ganesan Rajagopal Committed by Andrew Morton
Browse files

mm/memcontrol: export memcg->watermark via sysfs for v2 memcg 

We run a lot of automated tests when building our software and run into
OOM scenarios when the tests run unbounded.  v1 memcg exports
memcg->watermark as "memory.max_usage_in_bytes" in sysfs.  We use this
metric to heuristically limit the number of tests that can run in parallel
based on per test historical data.

This metric is currently not exported for v2 memcg and there is no other
easy way of getting this information.  getrusage() syscall returns
"ru_maxrss" which can be used as an approximation but that's the max RSS
of a single child process across all children instead of the aggregated
max for all child processes.  The only work around is to periodically poll
"memory.current" but that's not practical for short-lived one-off cgroups.

Hence, expose memcg->watermark as "memory.peak" for v2 memcg.

Link: https://lkml.kernel.org/r/20220507050916.GA13577@us192.sjc.aristanetworks.com


Signed-off-by: default avatarGanesan Rajagopal <rganesan@arista.com>
Acked-by: default avatarShakeel Butt <shakeelb@google.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Acked-by: default avatarRoman Gushchin <roman.gushchin@linux.dev>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: default avatarMichal Koutný <mkoutny@suse.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 78f39084

Documentation/admin-guide/cgroup-v2.rst

+7 −0
Original line number Diff line number Diff line
@@ -1229,6 +1229,13 @@ PAGE_SIZE multiple when read back. 
	the target cgroup. If less bytes are reclaimed than the

	specified amount, -EAGAIN is returned.



  memory.peak

	A read-only single value file which exists on non-root

	cgroups.



	The max memory usage recorded for the cgroup and its

	descendants since the creation of the cgroup.



  memory.oom.group

	A read-write single value file which exists on non-root

	cgroups.  The default value is "0".

mm/memcontrol.c

+13 −0
Original line number Diff line number Diff line
@@ -6103,6 +6103,14 @@ static u64 memory_current_read(struct cgroup_subsys_state *css, 
	return (u64)page_counter_read(&memcg->memory) * PAGE_SIZE;

}



static u64 memory_peak_read(struct cgroup_subsys_state *css,

			    struct cftype *cft)

{

	struct mem_cgroup *memcg = mem_cgroup_from_css(css);



	return (u64)memcg->memory.watermark * PAGE_SIZE;

}



static int memory_min_show(struct seq_file *m, void *v)

{

	return seq_puts_memcg_tunable(m,
@@ -6406,6 +6414,11 @@ static struct cftype memory_files[] = { 
		.flags = CFTYPE_NOT_ON_ROOT,

		.read_u64 = memory_current_read,

	},

	{

		.name = "peak",

		.flags = CFTYPE_NOT_ON_ROOT,

		.read_u64 = memory_peak_read,

	},

	{

		.name = "min",

		.flags = CFTYPE_NOT_ON_ROOT,