[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20200826150517.GS22869@dhcp22.suse.cz>
Date: Wed, 26 Aug 2020 17:05:17 +0200
From: Michal Hocko <mhocko@...e.com>
To: Xunlei Pang <xlpang@...ux.alibaba.com>
Cc: Johannes Weiner <hannes@...xchg.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Vladimir Davydov <vdavydov.dev@...il.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v2] mm: memcg: Fix memcg reclaim soft lockup
On Wed 26-08-20 21:47:02, Xunlei Pang wrote:
> 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 cond_resched() at the upper shrink_node_memcgs() to solve this
> issue, and any other possible issue like meomry.min protection.
I would just add
"
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.
"
> Suggested-by: Michal Hocko <mhocko@...e.com>
> Signed-off-by: Xunlei Pang <xlpang@...ux.alibaba.com>
Acked-by: Michal Hocko <mhocko@...e.com>
Thanks!
> ---
> mm/vmscan.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 99e1796..bbdc38b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2617,6 +2617,8 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
>
> mem_cgroup_calculate_protection(target_memcg, memcg);
>
> + cond_resched();
> +
> if (mem_cgroup_below_min(memcg)) {
> /*
> * Hard protection.
> --
> 1.8.3.1
--
Michal Hocko
SUSE Labs
Powered by blists - more mailing lists