* [merged] mm-memcg-fix-memcg-reclaim-soft-lockup.patch removed from -mm tree
@ 2020-09-12 16:23 akpm
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From: akpm @ 2020-09-12 16:23 UTC (permalink / raw)
To: chris, hannes, mhocko, mm-commits, xlpang
The patch titled
Subject: mm: memcg: fix memcg reclaim soft lockup
has been removed from the -mm tree. Its filename was
mm-memcg-fix-memcg-reclaim-soft-lockup.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Xunlei Pang <xlpang@linux.alibaba.com>
Subject: mm: memcg: fix memcg reclaim soft lockup
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.
Link: http://lkml.kernel.org/r/1598495549-67324-1-git-send-email-xlpang@linux.alibaba.com
Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>
Acked-by: Chris Down <chris@chrisdown.name>
Acked-by: Michal Hocko <mhocko@suse.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/vmscan.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/mm/vmscan.c~mm-memcg-fix-memcg-reclaim-soft-lockup
+++ a/mm/vmscan.c
@@ -2615,6 +2615,14 @@ static void shrink_node_memcgs(pg_data_t
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)) {
_
Patches currently in -mm which might be from xlpang@linux.alibaba.com are
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2020-09-12 16:23 [merged] mm-memcg-fix-memcg-reclaim-soft-lockup.patch removed from -mm tree akpm
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