From: Andrew Morton <akpm@linux-foundation.org>
To: Liu Shixin <liushixin2@huawei.com>
Cc: Yosry Ahmed <yosryahmed@google.com>,
Huang Ying <ying.huang@intel.com>,
Sachin Sant <sachinp@linux.ibm.com>,
Michal Hocko <mhocko@suse.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Kefeng Wang <wangkefeng.wang@huawei.com>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v6] mm: vmscan: try to reclaim swapcache pages if no swap space
Date: Wed, 4 Oct 2023 09:18:53 -0700 [thread overview]
Message-ID: <20231004091853.9be5aa562f65e0305e06b14c@linux-foundation.org> (raw)
In-Reply-To: <20230915083417.3190512-1-liushixin2@huawei.com>
On Fri, 15 Sep 2023 16:34:17 +0800 Liu Shixin <liushixin2@huawei.com> wrote:
> When spaces of swap devices are exhausted, only file pages can be
> reclaimed. But there are still some swapcache pages in anon lru list.
> This can lead to a premature out-of-memory.
>
> The problem is found with such step:
>
> Firstly, set a 9MB disk swap space, then create a cgroup with 10MB
> memory limit, then runs an program to allocates about 15MB memory.
>
> The problem occurs occasionally, which may need about 100 times [1].
>
> Fix it by checking number of swapcache pages in can_reclaim_anon_pages().
> If the number is not zero, return true and set swapcache_only to 1.
> When scan anon lru list in swapcache_only mode, non-swapcache pages will
> be skipped to isolate in order to accelerate reclaim efficiency.
>
> However, in swapcache_only mode, the scan count still increased when scan
> non-swapcache pages because there are large number of non-swapcache pages
> and rare swapcache pages in swapcache_only mode, and if the non-swapcache
> is skipped and do not count, the scan of pages in isolate_lru_folios() can
> eventually lead to hung task, just as Sachin reported [2].
>
> By the way, since there are enough times of memory reclaim before OOM, it
> is not need to isolate too much swapcache pages in one times.
>
mhocko earlier suspected this might impact global reclaim. Have you
looked into that further?
next prev parent reply other threads:[~2023-10-04 16:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-15 8:34 [PATCH v6] mm: vmscan: try to reclaim swapcache pages if no swap space Liu Shixin
2023-10-04 16:18 ` Andrew Morton [this message]
2023-10-07 6:26 ` Liu Shixin
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