From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932159AbcFQMjv (ORCPT ); Fri, 17 Jun 2016 08:39:51 -0400 Received: from mx2.suse.de ([195.135.220.15]:33317 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752847AbcFQMjt (ORCPT ); Fri, 17 Jun 2016 08:39:49 -0400 Subject: Re: [PATCH 27/27] mm: vmstat: Account per-zone stalls and pages skipped during reclaim To: Mel Gorman , Andrew Morton , Linux-MM References: <1465495483-11855-1-git-send-email-mgorman@techsingularity.net> <1465495483-11855-28-git-send-email-mgorman@techsingularity.net> Cc: Rik van Riel , Johannes Weiner , LKML From: Vlastimil Babka Message-ID: Date: Fri, 17 Jun 2016 14:39:46 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <1465495483-11855-28-git-send-email-mgorman@techsingularity.net> Content-Type: text/plain; charset=iso-8859-2; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/09/2016 08:04 PM, Mel Gorman wrote: > The vmstat allocstall was fairly useful in the general sense but > node-based LRUs change that. It's important to know if a stall was for an > address-limited allocation request as this will require skipping pages from > other zones. This patch adds pgstall_* counters to replace allocstall. The > sum of the counters will equal the old allocstall so it can be trivially > recalculated. A high number of address-limited allocation requests may > result in a lot of useless LRU scanning for suitable pages. > > As address-limited allocations require pages to be skipped, it's important > to know how much useless LRU scanning took place so this patch adds > pgskip* counters. This yields the following model > > 1. The number of address-space limited stalls can be accounted for (pgstall) > 2. The amount of useless work required to reclaim the data is accounted (pgskip) > 3. The total number of scans is available from pgscan_kswapd and pgscan_direct > so from that the ratio of useful to useless scans can be calculated. > > Signed-off-by: Mel Gorman Acked-by: Vlastimil Babka Nice work!