From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f198.google.com (mail-pf1-f198.google.com [209.85.210.198]) by kanga.kvack.org (Postfix) with ESMTP id 062FF8E0001 for ; Mon, 7 Jan 2019 04:01:34 -0500 (EST) Received: by mail-pf1-f198.google.com with SMTP id 68so42805982pfr.6 for ; Mon, 07 Jan 2019 01:01:33 -0800 (PST) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id j22sor36216490pll.8.2019.01.07.01.01.32 for (Google Transport Security); Mon, 07 Jan 2019 01:01:32 -0800 (PST) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 12.2 \(3445.102.3\)) Subject: Re: memory cgroup pagecache and inode problem From: Fam Zheng In-Reply-To: <20190107085316.GY31793@dhcp22.suse.cz> Date: Mon, 7 Jan 2019 17:01:27 +0800 Content-Transfer-Encoding: quoted-printable Message-Id: References: <15614FDC-198E-449B-BFAF-B00D6EF61155@bytedance.com> <97A4C2CA-97BA-46DB-964A-E44410BB1730@bytedance.com> <20190107085316.GY31793@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Fam Zheng , Yang Shi , cgroups@vger.kernel.org, Linux MM , tj@kernel.org, Johannes Weiner , lizefan@huawei.com, Vladimir Davydov , duanxiongchun@bytedance.com, =?utf-8?B?5byg5rC46IKD?= , liuxiaozhou@bytedance.com > On Jan 7, 2019, at 16:53, Michal Hocko wrote: >=20 > On Mon 07-01-19 13:10:17, Fam Zheng wrote: >>=20 >>=20 >>> On Jan 5, 2019, at 03:36, Yang Shi wrote: >>>=20 >>>=20 >>> drop_caches would drop all page caches globally. You may not want to >>> drop the page caches used by other memcgs. >>=20 >> We=E2=80=99ve tried your async force_empty patch (with a modification = to default it to true to make it transparently enabled for the sake of = testing), and for the past few days the stale mem cgroups still = accumulate, up to 40k. >>=20 >> We=E2=80=99ve double checked that the force_empty routines are = invoked when a mem cgroup is offlined. But this doesn=E2=80=99t look = very effective so far. Because, once we do `echo 1 > = /proc/sys/vm/drop_caches`, all the groups immediately go away. >>=20 >> This is a bit unexpected. >>=20 >> Yang, could you hint what are missing in the force_empty operation, = compared to a blanket drop cache? >=20 > I would suspect that not all slab pages holding dentries and inodes = got > reclaimed during the slab shrinking inoked by the direct reclaimed > triggered by force emptying. I don=E2=80=99t think so, we=E2=80=99ve ensured = cgroup.memory=3Dnokmem,nosocket first, as observed with the result of = =E2=80=98echo 1=E2=80=99 command. It=E2=80=99s not slabs but the page = caches holding mem cgroups. It might well be that we=E2=80=99ve missing 68600f623d6, though. We=E2=80=99= ll check it. Thanks, Fam > --=20 > Michal Hocko > SUSE Labs