On Tue, Jun 21, 2016 at 01:16:51PM +0300, Vladimir Davydov wrote:

On Fri, Jun 17, 2016 at 12:25:16PM -0400, Johannes Weiner wrote:

quoted

After this patch, the IDs get released upon cgroup destruction and the
cache and css objects get released once memory reclaim kicks in.

With 65K cgroups it will take the reclaimer a substantial amount of time
to iterate over all of them, which might result in latency spikes.
Probably, to avoid that, we could move pages from a dead cgroup's lru to
its parent's one on offline while still leaving dead cgroups pinned,
like we do in case of list_lru entries.

Yep, that is true. list_lru is a bit easier because the walker stays
in the context of the original LRU list, whereas the cache/anon LRUs
are not. We'd have to have mem_cgroup_page_lruvec() etc. do a parent
walk to find the closest live ancestor. Maybe you have a better idea?

But it's definitely worth considering. I'll think more about it.

quoted

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Reviewed-by: Vladimir Davydov <redacted>

Thanks!

quoted

+static struct idr mem_cgroup_idr;

static DEFINE_IDR(mem_cgroup_idr);

Oops, good catch. Andrew, could you kindly fold this?

From d1261ede8f975a5fccb2e9125562260e4b4b4f3d Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Tue, 21 Jun 2016 11:36:13 -0400
Subject: [PATCH] mm: memcontrol: fix cgroup creation failure after many small
 jobs fix

init the IDR

Reported-by: Vladimir Davydov <redacted>
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
 mm/memcontrol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index dc92b2df2585..b0de1342eab2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

@@ -4081,7 +4081,7 @@ static struct cftype mem_cgroup_legacy_files[] = {
  * those references are manageable from userspace.
  */
 
-static struct idr mem_cgroup_idr;
+static DEFINE_IDR(mem_cgroup_idr);
 
 static void mem_cgroup_id_get(struct mem_cgroup *memcg)
 {

-- 
2.8.3

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