From: Michal Hocko <mhocko@suse.com>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Dave Hansen <dave.hansen@intel.com>,
Ying Huang <ying.huang@intel.com>,
linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] mm: Fix dropped memcg from mem cgroup soft limit tree
Date: Wed, 10 Feb 2021 10:47:44 +0100 [thread overview]
Message-ID: <YCOrwHvktsN5Kuc+@dhcp22.suse.cz> (raw)
In-Reply-To: <d50e3bb513845d1f7816b94733576ce6f798682a.1612902157.git.tim.c.chen@linux.intel.com>
On Tue 09-02-21 12:29:45, Tim Chen wrote:
> During soft limit memory reclaim, we will temporarily remove the target
> mem cgroup from the cgroup soft limit tree. We then perform memory
> reclaim, update the memory usage excess count and re-insert the mem
> cgroup back into the mem cgroup soft limit tree according to the new
> memory usage excess count.
>
> However, when memory reclaim failed for a maximum number of attempts
> and we bail out of the reclaim loop, we forgot to put the target mem
> cgroup chosen for next reclaim back to the soft limit tree. This prevented
> pages in the mem cgroup from being reclaimed in the future even though
> the mem cgroup exceeded its soft limit. Fix the logic and put the mem
> cgroup back on the tree when page reclaim failed for the mem cgroup.
>
> Reviewed-by: Ying Huang <ying.huang@intel.com>
> Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
It seems this goes all the way to when it has been introduced by
4e41695356fb ("memory controller: soft limit reclaim on contention").
Please add a Fixes tag pointing to the above one. While this looks like
a rare event to happen because there should be some reclaimable memory
usually.
Acked-by: Michal Hocko <mhocko@suse.com>
Thanks!
> ---
> mm/memcontrol.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index ed5cc78a8dbf..a51bf90732cb 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3505,8 +3505,12 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
> loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS))
> break;
> } while (!nr_reclaimed);
> - if (next_mz)
> + if (next_mz) {
> + spin_lock_irq(&mctz->lock);
> + __mem_cgroup_insert_exceeded(next_mz, mctz, excess);
> + spin_unlock_irq(&mctz->lock);
> css_put(&next_mz->memcg->css);
> + }
> return nr_reclaimed;
> }
>
> --
> 2.20.1
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2021-02-10 9:50 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-09 20:29 [PATCH 0/3] Soft limit memory management bug fixes Tim Chen
2021-02-09 20:29 ` [PATCH 1/3] mm: Fix dropped memcg from mem cgroup soft limit tree Tim Chen
2021-02-10 9:47 ` Michal Hocko [this message]
2021-02-09 20:29 ` [PATCH 2/3] mm: Force update of mem cgroup soft limit tree on usage excess Tim Chen
2021-02-10 9:51 ` Michal Hocko
2021-02-09 20:29 ` [PATCH 3/3] mm: Fix missing mem cgroup soft limit tree updates Tim Chen
2021-02-09 22:22 ` Johannes Weiner
2021-02-09 22:34 ` Tim Chen
2021-02-10 10:08 ` Michal Hocko
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