From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-f199.google.com (mail-pl1-f199.google.com [209.85.214.199]) by kanga.kvack.org (Postfix) with ESMTP id 4E1A86B02BC for ; Thu, 25 Oct 2018 15:44:45 -0400 (EDT) Received: by mail-pl1-f199.google.com with SMTP id f5-v6so6330907plf.11 for ; Thu, 25 Oct 2018 12:44:45 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id r24-v6si8765721pgv.380.2018.10.25.12.44.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Oct 2018 12:44:44 -0700 (PDT) Date: Thu, 25 Oct 2018 12:44:42 -0700 From: Andrew Morton Subject: Re: [RFC PATCH] mm: don't reclaim inodes with many attached pages Message-Id: <20181025124442.5513d282273786369bbb7460@linux-foundation.org> In-Reply-To: <20181025092352.GP18839@dhcp22.suse.cz> References: <20181023164302.20436-1-guro@fb.com> <20181024151950.36fe2c41957d807756f587ca@linux-foundation.org> <20181025092352.GP18839@dhcp22.suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Roman Gushchin , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Kernel Team , Rik van Riel , Randy Dunlap , Sasha Levin On Thu, 25 Oct 2018 11:23:52 +0200 Michal Hocko wrote: > 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. Yup. Sasha, can you please take care of this?