From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) by kanga.kvack.org (Postfix) with ESMTP id 3E1A76B031F for ; Fri, 26 Oct 2018 11:57:20 -0400 (EDT) Received: by mail-qk1-f199.google.com with SMTP id w6-v6so1428570qka.15 for ; Fri, 26 Oct 2018 08:57:20 -0700 (PDT) Received: from mx0b-00082601.pphosted.com (mx0b-00082601.pphosted.com. [67.231.153.30]) by mx.google.com with ESMTPS id f23-v6si634097qvd.124.2018.10.26.08.57.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 26 Oct 2018 08:57:19 -0700 (PDT) From: Roman Gushchin Subject: Re: [RFC PATCH] mm: don't reclaim inodes with many attached pages Date: Fri, 26 Oct 2018 15:56:55 +0000 Message-ID: <20181026155652.GA7647@tower.DHCP.thefacebook.com> References: <20181023164302.20436-1-guro@fb.com> <20181026085735.GZ18839@dhcp22.suse.cz> In-Reply-To: <20181026085735.GZ18839@dhcp22.suse.cz> Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Kernel Team , Rik van Riel , Randy Dunlap , Andrew Morton , "dairinin@gmail.com" On Fri, Oct 26, 2018 at 10:57:35AM +0200, Michal Hocko wrote: > Spock doesn't seem to be cced here - fixed now >=20 > On Tue 23-10-18 16:43:29, Roman Gushchin wrote: > > Spock reported that the commit 172b06c32b94 ("mm: slowly shrink slabs > > with a relatively small number of objects") leads to a regression on > > his setup: periodically the majority of the pagecache is evicted > > without an obvious reason, while before the change the amount of free > > memory was balancing around the watermark. > >=20 > > The reason behind is that the mentioned above change created some > > minimal background pressure on the inode cache. The problem is that > > if an inode is considered to be reclaimed, all belonging pagecache > > page are stripped, no matter how many of them are there. So, if a huge > > multi-gigabyte file is cached in the memory, and the goal is to > > reclaim only few slab objects (unused inodes), we still can eventually > > evict all gigabytes of the pagecache at once. > >=20 > > The workload described by Spock has few large non-mapped files in the > > pagecache, so it's especially noticeable. > >=20 > > To solve the problem let's postpone the reclaim of inodes, which have > > more than 1 attached page. Let's wait until the pagecache pages will > > be evicted naturally by scanning the corresponding LRU lists, and only > > then reclaim the inode structure. >=20 > Has this actually fixed/worked around the issue? Spock wrote this earlier to me directly. I believe I can quote it here: "Patch applied, looks good so far. System behaves like it was with pre-4.18.15 kernels. Also tried to add some user-level tests to the geneic background activity, = like - stat'ing a bunch of files - streamed read several large files at once on ext4 and XFS - random reads on the whole collection with a read size of 16K I will be monitoring while fragmentation stacks up and report back if something bad happens." Spock, please let me know if you have any new results. Thanks!