From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f69.google.com (mail-ed1-f69.google.com [209.85.208.69]) by kanga.kvack.org (Postfix) with ESMTP id 9F9676B0276 for ; Thu, 25 Oct 2018 05:23:56 -0400 (EDT) Received: by mail-ed1-f69.google.com with SMTP id k17-v6so4285933edr.18 for ; Thu, 25 Oct 2018 02:23:56 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id l33-v6si523014edc.77.2018.10.25.02.23.55 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Oct 2018 02:23:55 -0700 (PDT) Date: Thu, 25 Oct 2018 11:23:52 +0200 From: Michal Hocko Subject: Re: [RFC PATCH] mm: don't reclaim inodes with many attached pages Message-ID: <20181025092352.GP18839@dhcp22.suse.cz> References: <20181023164302.20436-1-guro@fb.com> <20181024151950.36fe2c41957d807756f587ca@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181024151950.36fe2c41957d807756f587ca@linux-foundation.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Roman Gushchin , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Kernel Team , Rik van Riel , Randy Dunlap On Wed 24-10-18 15:19:50, Andrew Morton wrote: > On Tue, 23 Oct 2018 16:43:29 +0000 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. > > > > 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. > > > > The workload described by Spock has few large non-mapped files in the > > pagecache, so it's especially noticeable. > > > > 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. > > Is this regression serious enough to warrant fixing 4.19.1? Let's not forget about stable tree(s) which backported 172b06c32b94. I would suggest reverting there. -- Michal Hocko SUSE Labs