From: Julius Hemanth Pitti <jpitti@cisco.com>
To: hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com,
akpm@linux-foundation.org
Cc: cgroups@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, xe-linux-external@cisco.com,
Julius Hemanth Pitti <jpitti@cisco.com>
Subject: [PATCH] mm: memcg: yield cpu when we fail to charge pages
Date: Tue, 8 Sep 2020 11:50:51 -0700 [thread overview]
Message-ID: <20200908185051.62420-1-jpitti@cisco.com> (raw)
For non root CG, in try_charge(), we keep trying
to charge until we succeed. On non-preemptive
kernel, when we are OOM, this results in holding
CPU forever.
On SMP systems, this doesn't create a big problem
because oom_reaper get a change to kill victim
and make some free pages. However on a single-core
CPU (or cases where oom_reaper pinned to same CPU
where try_charge is executing), oom_reaper shall
never get scheduled and we stay in try_charge forever.
Steps to repo this on non-smp:
1. mount -t tmpfs none /sys/fs/cgroup
2. mkdir /sys/fs/cgroup/memory
3. mount -t cgroup none /sys/fs/cgroup/memory -o memory
4. mkdir /sys/fs/cgroup/memory/0
5. echo 40M > /sys/fs/cgroup/memory/0/memory.limit_in_bytes
6. echo $$ > /sys/fs/cgroup/memory/0/tasks
7. stress -m 5 --vm-bytes 10M --vm-hang 0
Signed-off-by: Julius Hemanth Pitti <jpitti@cisco.com>
---
mm/memcontrol.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0d6f3ea86738..4620d70267cb 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2652,6 +2652,8 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
if (fatal_signal_pending(current))
goto force;
+ cond_resched();
+
/*
* keep retrying as long as the memcg oom killer is able to make
* a forward progress or bypass the charge if the oom killer
--
2.17.1
next reply other threads:[~2020-09-08 18:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-08 18:50 Julius Hemanth Pitti [this message]
2020-09-08 19:21 ` [PATCH] mm: memcg: yield cpu when we fail to charge pages Roman Gushchin
2020-09-08 19:28 ` Julius Hemanth Pitti (jpitti)
2020-09-14 4:15 ` Xunlei Pang
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