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authorYosry Ahmed <yosryahmed@google.com>2023-03-30 22:17:56 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-04-19 02:29:49 +0300
commita2174e95cce5e65ee49c60368434aaae944ff1af (patch)
tree7102fb04b6edb19bb5a14681b6cb2f9a219fdad6 /mm/memcontrol.c
parent92fbbc7202ac4fb16250dc91c88211814ae2190b (diff)
downloadlinux-a2174e95cce5e65ee49c60368434aaae944ff1af.tar.xz
memcg: do not flush stats in irq context
Currently, the only context in which we can invoke an rstat flush from irq context is through mem_cgroup_usage() on the root memcg when called from memcg_check_events(). An rstat flush is an expensive operation that should not be done in irq context, so do not flush stats and use the stale stats in this case. Arguably, usage threshold events are not reliable on the root memcg anyway since its usage is ill-defined. Link: https://lkml.kernel.org/r/20230330191801.1967435-4-yosryahmed@google.com Signed-off-by: Yosry Ahmed <yosryahmed@google.com> Suggested-by: Johannes Weiner <hannes@cmpxchg.org> Suggested-by: Shakeel Butt <shakeelb@google.com> Acked-by: Shakeel Butt <shakeelb@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Josef Bacik <josef@toxicpanda.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Michal Koutný <mkoutny@suse.com> Cc: Muchun Song <muchun.song@linux.dev> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Tejun Heo <tj@kernel.org> Cc: Vasily Averin <vasily.averin@linux.dev> Cc: Zefan Li <lizefan.x@bytedance.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
-rw-r--r--mm/memcontrol.c16
1 files changed, 15 insertions, 1 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a01f062e7007..5040db9a76a6 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3670,7 +3670,21 @@ static unsigned long mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
unsigned long val;
if (mem_cgroup_is_root(memcg)) {
- mem_cgroup_flush_stats();
+ /*
+ * We can reach here from irq context through:
+ * uncharge_batch()
+ * |--memcg_check_events()
+ * |--mem_cgroup_threshold()
+ * |--__mem_cgroup_threshold()
+ * |--mem_cgroup_usage
+ *
+ * rstat flushing is an expensive operation that should not be
+ * done from irq context; use stale stats in this case.
+ * Arguably, usage threshold events are not reliable on the root
+ * memcg anyway since its usage is ill-defined.
+ */
+ if (in_task())
+ mem_cgroup_flush_stats();
val = memcg_page_state(memcg, NR_FILE_PAGES) +
memcg_page_state(memcg, NR_ANON_MAPPED);
if (swap)