From: Xunlei Pang <xlpang@linux.alibaba.com>
To: Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Chris Down <chris@chrisdown.name>
Cc: Xunlei Pang <xlpang@linux.alibaba.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH v3] mm: memcg: Fix memcg reclaim soft lockup
Date: Thu, 27 Aug 2020 10:32:29 +0800 [thread overview]
Message-ID: <1598495549-67324-1-git-send-email-xlpang@linux.alibaba.com> (raw)
We've met softlockup with "CONFIG_PREEMPT_NONE=y", when
the target memcg doesn't have any reclaimable memory.
It can be easily reproduced as below:
watchdog: BUG: soft lockup - CPU#0 stuck for 111s![memcg_test:2204]
CPU: 0 PID: 2204 Comm: memcg_test Not tainted 5.9.0-rc2+ #12
Call Trace:
shrink_lruvec+0x49f/0x640
shrink_node+0x2a6/0x6f0
do_try_to_free_pages+0xe9/0x3e0
try_to_free_mem_cgroup_pages+0xef/0x1f0
try_charge+0x2c1/0x750
mem_cgroup_charge+0xd7/0x240
__add_to_page_cache_locked+0x2fd/0x370
add_to_page_cache_lru+0x4a/0xc0
pagecache_get_page+0x10b/0x2f0
filemap_fault+0x661/0xad0
ext4_filemap_fault+0x2c/0x40
__do_fault+0x4d/0xf9
handle_mm_fault+0x1080/0x1790
It only happens on our 1-vcpu instances, because there's no chance
for oom reaper to run to reclaim the to-be-killed process.
Add a cond_resched() at the upper shrink_node_memcgs() to solve this
issue, this will mean that we will get a scheduling point for each
memcg in the reclaimed hierarchy without any dependency on the
reclaimable memory in that memcg thus making it more predictable.
Acked-by: Chris Down <chris@chrisdown.name>
Acked-by: Michal Hocko <mhocko@suse.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>
---
mm/vmscan.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 99e1796..9727dd8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2615,6 +2615,14 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
unsigned long reclaimed;
unsigned long scanned;
+ /*
+ * This loop can become CPU-bound when target memcgs
+ * aren't eligible for reclaim - either because they
+ * don't have any reclaimable pages, or because their
+ * memory is explicitly protected. Avoid soft lockups.
+ */
+ cond_resched();
+
mem_cgroup_calculate_protection(target_memcg, memcg);
if (mem_cgroup_below_min(memcg)) {
--
1.8.3.1
next reply other threads:[~2020-08-27 2:32 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-27 2:32 Xunlei Pang [this message]
2020-08-27 14:00 ` [PATCH v3] mm: memcg: Fix memcg reclaim soft lockup Johannes Weiner
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