From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7BC5CC282C8 for ; Mon, 28 Jan 2019 11:04:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5025121736 for ; Mon, 28 Jan 2019 11:04:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726913AbfA1LD7 (ORCPT ); Mon, 28 Jan 2019 06:03:59 -0500 Received: from outbound-smtp02.blacknight.com ([81.17.249.8]:33025 "EHLO outbound-smtp02.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726654AbfA1LD7 (ORCPT ); Mon, 28 Jan 2019 06:03:59 -0500 Received: from mail.blacknight.com (pemlinmail05.blacknight.ie [81.17.254.26]) by outbound-smtp02.blacknight.com (Postfix) with ESMTPS id DB1CF98B0D for ; Mon, 28 Jan 2019 11:03:56 +0000 (UTC) Received: (qmail 32514 invoked from network); 28 Jan 2019 11:03:56 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[37.228.225.79]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 28 Jan 2019 11:03:56 -0000 Date: Mon, 28 Jan 2019 11:03:55 +0000 From: Mel Gorman To: valdis.kletnieks@vt.edu, Pavel Machek Cc: kernel list , Andrew Morton , vbabka@suse.cz, aarcange@redhat.com, rientjes@google.com, mhocko@kernel.org, zi.yan@cs.rutgers.edu, hannes@cmpxchg.org, Jan Kara Subject: Re: [regression -next0117] What is kcompactd and why is he eating 100% of my cpu? Message-ID: <20190128110355.GC9565@techsingularity.net> References: <20190126200005.GB27513@amd> <12171.1548557813@turing-police.cc.vt.edu> <20190127141556.GB9565@techsingularity.net> <20190127160027.GA9340@amd> <13417.1548624994@turing-police.cc.vt.edu> <20190128091627.GA27972@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20190128091627.GA27972@quack2.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 28, 2019 at 10:16:27AM +0100, Jan Kara wrote: > On Sun 27-01-19 16:36:34, valdis.kletnieks@vt.edu wrote: > > On Sun, 27 Jan 2019 17:00:27 +0100, Pavel Machek said: > > > > > I've noticed this as well on earlier kernels (next-20181224 to 20190115) > > > > > Some more info: > > > > > 1) echo 3 > /proc/sys/vm/drop_caches unwedges kcompactd in 1-3 seconds. > > > > This aspect is curious as it indicates that kcompactd could potentially > > > > be infinite looping but it's not something I've experienced myself. By > > > > any chance is there a preditable reproduction case for this? > > > > > > I seen it exactly once, so not sure how reproducible this is. x86-32 > > > machine, running chromium browser, so yes, there was some swapping > > > involved. > > > > I don't have a surefire replicator, but my laptop (x86_64, so it's not a 32-bit > > only issue) triggers it fairly often, up to multiple times a day. Doesn't seem to > > be just the Chrome browser that triggers it - usually I'm doing other stuff as > > well, like a compile or similar. The fact that 'drop_caches' clears it makes me > > wonder if we're hitting a corner case where cache data isn't being automatically > > cleared and clogging something up. > > So my buffer_migrate_page_norefs() is certainly buggy in its current > incarnation (as a result block device page cache is not migratable at all). > I've sent Andrew a patch over week ago but so far it got ignored. The patch > is attached, can you give it a try whether it changes something for you? > Thanks! > Definetly worth trying and hopefully both the migration and compaction patches sync up soon. In the event this patch does not help, I would appreciate the following 1) A trace while kcompactd is pegged at 100% trace-cmd record -a -e compaction -e migrate -e kmem:mm_page_alloc -e vmscan:mm_vmscan_kswapd_wake -e vmscan:mm_vmscan_kswapd_sleep sleep 10 Compress the resulting trace.dat and email it to me. If it's too big for a reasonable email, drop "-e kmem:mm_page_alloc" from the command line and it should be a more reasonable size. If not, reduce the sleep time to gather a shorter inverval. 2) Sample stack traces of kcompact while pegged at 100% echo -n > /tmp/kcompactd-stack; for i in `seq 1 100`; do echo sample $i >> /tmp/kcompactd-stack; cat /proc/`pidof kcompactd0`/stack >> /tmp/kcompactd-stack; done; gzip -f /tmp/kcompactd-stack And mail me the resulting /tmp/kcompactd-stack.gz Thanks. -- Mel Gorman SUSE Labs