From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752261AbdBCO7y (ORCPT ); Fri, 3 Feb 2017 09:59:54 -0500 Received: from mx2.suse.de ([195.135.220.15]:35407 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751605AbdBCO7x (ORCPT ); Fri, 3 Feb 2017 09:59:53 -0500 Date: Fri, 3 Feb 2017 15:59:48 +0100 From: Michal Hocko To: vinayak menon Cc: Vinayak Menon , Andrew Morton , Johannes Weiner , mgorman@techsingularity.net, vbabka@suse.cz, Rik van Riel , vdavydov.dev@gmail.com, anton.vorontsov@linaro.org, Minchan Kim , shashim@codeaurora.org, "linux-mm@kvack.org" , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2 v3] mm: vmscan: do not pass reclaimed slab to vmpressure Message-ID: <20170203145947.GD19325@dhcp22.suse.cz> References: <1485504817-3124-1-git-send-email-vinmenon@codeaurora.org> <1485853328-7672-1-git-send-email-vinmenon@codeaurora.org> <20170202104422.GF22806@dhcp22.suse.cz> <20170202104808.GG22806@dhcp22.suse.cz> <20170202115222.GH22806@dhcp22.suse.cz> <20170202160145.GK22806@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 03-02-17 10:56:42, vinayak menon wrote: > On Thu, Feb 2, 2017 at 9:31 PM, Michal Hocko wrote: > > > > Why would you like to chose and kill a task when the slab reclaim can > > still make sufficient progres? Are you sure that the slab contribution > > to the stats makes all the above happening? > > > I agree that a task need not be killed if sufficient progress is made > in reclaiming > memory say from slab. But here it looks like we have an impact because of just > increasing the reclaimed without touching the scanned. It could be because of > disimilar costs or not adding adding cost. I agree that vmpressure is > only a reasonable > estimate which does not already include few other costs, but I am not > sure whether it is ok > to add another element which further increases that disparity. > We noticed this problem when moving from 3.18 to 4.4 kernel version. With the > same workload, the vmpressure events differ between 3.18 and 4.4 causing the > above mentioned problem. And with this patch on 4.4 we get the same results > as in 3,18. So the slab contribution to stats is making a difference. Please document that in the changelog along with description of the workload that is affected. Ideally also add some data from /proc/vmstat so that we can see the reclaim activity. -- Michal Hocko SUSE Labs