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Wed, 23 Aug 2023 08:29:55 -0700 (PDT) MIME-Version: 1.0 References: <20230822024901.2412520-1-liushixin2@huawei.com> <50c49baf-d04a-f1e3-0d0e-7bb8e22c3889@huawei.com> In-Reply-To: From: Yosry Ahmed Date: Wed, 23 Aug 2023 08:29:19 -0700 Message-ID: Subject: Re: [PATCH v2] mm: vmscan: reclaim anon pages if there are swapcache pages To: Michal Hocko Cc: Liu Shixin , Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , wangkefeng.wang@huawei.com, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: nfb76pu1zukpamrn59zhxu35dmnhb43n X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: E970F40013 X-Rspam-User: X-HE-Tag: 1692804596-850288 X-HE-Meta: U2FsdGVkX1/nM/4txgLAyewyw6ii520DjVUrn+c+eZ5lwf5T4sD1RSUVvzloPqUvKJlgi/wifqqqnopPPH0ic73EpRcFoxA+MVd4AKwWOXZs7E0aHvtRZcJRY3Zlb/uBaXprY7xXhsrQNEvdFFInU3r9pd6kOIbSo4F4kIS9EZXskoCrHVAW6nNL0HBJJNjl9/a04olrQaR3WDmYLisRpmM5ZynUEredZINrD6/Vt0A+wPkexIFxM8PXZpEFi1CLlLdfgsa6laFOuaO3vYyXJBuEI+eeue2qm66sNwuY6kekq2W3tLwNONOU9QZlK5XIukzv00Ux99BI6GaSawu/FotYhFSmMasuuq/KUe5E80XqXTMasiSsxVb6oOUXboqEkW4G8yUaFHqYRncoH20yy2iHf3xP7GSAn3o8n/PX1R6aVMFDYHDxvNTNSiRrBAVRHv4wo0xrOpBDjP8nCmbOYLP55IQe4/u2NpL2hxyc0+4upiJVOrdYsGFaEi/mYcqsLQVGqfiveR1BDHbIpOgOVX8siCPm7Er7ehKIx2rRViVZn/WmwgCGdTVprX0Z+Zm0g9/x3zTYavhl6hfaJwBUuBYWxhHktlIEbnaRQ9jFWobkuAuVHnFm1h5Y1FLiDGwjrHU1D2HuCWYTP4SN4/jWsBTUzGOE5m9le8+Y+0vfMu2s38s2oMdIhqmzIkfMO5TLl1zZYHJf7eB3OGFRc/PrbakVhsN+CW8j4V6FX2Qaeh3/F/YIzzcJ5P1gbhfRzCs7dKaJaw7O3t6CHDEPsSJAXb21sGWRIL1CGFiU0zgGc1+rU0dkvx7rLdvyuFh3FLWMTrpFIyCErCET1UWoLacyIH0R/bLAjNCXoFA1Dp8Hg41Hwt94krQQpOELMIsBHXlEVKCfCejDIlq4qpItCEn7xSEKIR6Yzm4dLeN+y6sPN0HXF9F5wc5sQjZlzXUbEAVvGJvCi59/fsUHAWejY9n 9h/R11Gi wwHWG2R09roWMbfYOVKW2dV6cm4Zt5X2bQwv5gDYsU6cPSfkl+1zNhvKc8VdzIDG875BiAqyVMh+JNaMfbdB/1gIm637r5lBDs10e5gHvjO3qgwz7TirBfO7CAtUpZ8ztMrOE/rmNCy82LMGCObd8uCK0jhE6fpM6a5Q/Y7n1PDzBRZ/3JnFfUg3yr41L9qzHFwWxnUozfbXpDLNe0MoPnSmAluG/zcW5eRqouuUDec0mp88t0FSF0I7Z9dTrkHT9elpqfw5FNyd2euZJ6kapahzWQtW4ACYX1qfPHjrtw9+et/WMQwVlAHA12Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Aug 23, 2023 at 6:12=E2=80=AFAM Michal Hocko wrot= e: > > On Wed 23-08-23 10:00:58, Liu Shixin wrote: > > > > > > On 2023/8/23 0:35, Yosry Ahmed wrote: > > > On Mon, Aug 21, 2023 at 6:54=E2=80=AFPM Liu Shixin wrote: > > >> When spaces of swap devices are exhausted, only file pages can be re= claimed. > > >> But there are still some swapcache pages in anon lru list. This can = lead > > >> to a premature out-of-memory. > > >> > > >> This problem can be fixed by checking number of swapcache pages in > > >> can_reclaim_anon_pages(). For memcg v2, there are swapcache stat tha= t can > > >> be used directly. For memcg v1, use total_swapcache_pages() instead,= which > > >> may not accurate but can solve the problem. > > > Interesting find. I wonder if we really don't have any handling of > > > this situation. > > I have alreadly test this problem and can confirm that it is a real pro= blem. > > With 9MB swap space and 10MB mem_cgroup limit=EF=BC=8Cwhen allocate 15M= B memory, > > there is a probability that OOM occurs. > > Could you be more specific about the test and the oom report? I actually couldn't reproduce it using 9MB of zram and a cgroup with a 10MB limit trying to allocate 15MB of tmpfs, no matter how many repetitions I do. > > -- > Michal Hocko > SUSE Labs