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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 A03B8CA9EBD for ; Fri, 25 Oct 2019 11:43:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7883E21D7B for ; Fri, 25 Oct 2019 11:43:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1572003836; bh=oGf8963/ffh0SXo4J75BA8mJA7B6+pkAReflvOi0+gw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=x5G5gBTwA2jZQi0K3YlN83cZ5AbU9JYxo9xpVTTmYZT1oZNAWlb7rnaDivweWfgNO Q8d1Hdq420rUBCYErs8Qsw5pyZRlC15Q7sExssEvnFhu391PvOfjbIzamSn2kTzAYm I/Nep00Yjx998P3YIc9ugtGXSwsEAzif01Mf1iQw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2501993AbfJYLnz (ORCPT ); Fri, 25 Oct 2019 07:43:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:41398 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2501933AbfJYLnz (ORCPT ); Fri, 25 Oct 2019 07:43:55 -0400 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 Content-Transfer-Encoding: 8bit In-Reply-To: <192965B3-B446-499C-AEE8-DFF087D46B87@lca.pw> 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 Fri 25-10-19 07:18:37, Qian Cai wrote: >  > > > On Oct 25, 2019, at 3:26 AM, Michal Hocko wrote: > > > > Considering the pagetypeinfo is a debugging tool we do not really need > > exact numbers here. The primary reason to look at the outuput is to see > > how pageblocks are spread among different migratetypes and low number of > > pages is much more interesting therefore putting a bound on the number > > of pages on the free_list sounds like a reasonable tradeoff. > > > > The new output will simply tell > > [...] > > Node 6, zone Normal, type Movable >100000 >100000 >100000 >100000 41019 31560 23996 10054 3229 983 648 > > 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. -- Michal Hocko SUSE Labs