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=MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 77C79CA9EA0 for ; Fri, 25 Oct 2019 11:43:56 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 425A52070B for ; Fri, 25 Oct 2019 11:43:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 425A52070B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CC6886B0003; Fri, 25 Oct 2019 07:43:55 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C770F6B0006; Fri, 25 Oct 2019 07:43:55 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B663B6B0007; Fri, 25 Oct 2019 07:43:55 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0212.hostedemail.com [216.40.44.212]) by kanga.kvack.org (Postfix) with ESMTP id 95D586B0003 for ; Fri, 25 Oct 2019 07:43:55 -0400 (EDT) Received: from smtpin23.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 1ED276123 for ; Fri, 25 Oct 2019 11:43:55 +0000 (UTC) X-FDA: 76082122830.23.oil49_79795a908382d X-HE-Tag: oil49_79795a908382d X-Filterd-Recvd-Size: 3076 Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by imf22.hostedemail.com (Postfix) with ESMTP for ; Fri, 25 Oct 2019 11:43:54 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id EEFC7AC59; Fri, 25 Oct 2019 11:43:52 +0000 (UTC) Date: Fri, 25 Oct 2019 13:43:50 +0200 From: Michal Hocko To: Qian Cai Cc: Andrew Morton , Mel Gorman , Waiman Long , Johannes Weiner , Roman Gushchin , Vlastimil Babka , Konstantin Khlebnikov , Jann Horn , Song Liu , Greg Kroah-Hartman , Rafael Aquini , linux-mm@kvack.org, LKML Subject: Re: [PATCH 2/2] mm, vmstat: reduce zone->lock holding time by /proc/pagetypeinfo Message-ID: <20191025114350.GD17610@dhcp22.suse.cz> References: <192965B3-B446-499C-AEE8-DFF087D46B87@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <192965B3-B446-499C-AEE8-DFF087D46B87@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri 25-10-19 07:18:37, Qian Cai wrote: > =EF=BB=BF >=20 > > On Oct 25, 2019, at 3:26 AM, Michal Hocko wrote: > >=20 > > Considering the pagetypeinfo is a debugging tool we do not really nee= d > > exact numbers here. The primary reason to look at the outuput is to s= ee > > how pageblocks are spread among different migratetypes and low number= of > > pages is much more interesting therefore putting a bound on the numbe= r > > of pages on the free_list sounds like a reasonable tradeoff. > >=20 > > The new output will simply tell > > [...] > > Node 6, zone Normal, type Movable >100000 >100000 >100000 >= 100000 41019 31560 23996 10054 3229 983 648 >=20 > It was mentioned that developers could use this file is to see the > movement of those numbers for debugging, so this supposed to introduce > regressions as there is no movement anymore for those 100k+ items? Can you provide an explicit example please? As the changelog mentions it is the "low numbers" that is really interesting when debugging fragmentation issues. Because we are running out of a respective migrate type and it is interesting to see why and what compaction is doing etc. Having more than 100k pages on the respective migrate type list is a good sign that the migrate type is not in problems. Comparing multiple migrate types with >100k pages doesn't really need a large precision AFAIU. Now, I do agree that some debugging tools might get confused by > in the output but can we wait for reports and see whether anybody actually cares? It is more likely that fixing one off debugging tools wouldn't be a big deal. --=20 Michal Hocko SUSE Labs