From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f200.google.com (mail-wr0-f200.google.com [209.85.128.200]) by kanga.kvack.org (Postfix) with ESMTP id 1342B6B0033 for ; Mon, 2 Oct 2017 03:23:50 -0400 (EDT) Received: by mail-wr0-f200.google.com with SMTP id t76so2748084wrc.12 for ; Mon, 02 Oct 2017 00:23:50 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id r75si7421495wmf.261.2017.10.02.00.23.47 for (version=TLS1 cipher=AES128-SHA bits=128/128); Mon, 02 Oct 2017 00:23:47 -0700 (PDT) Date: Mon, 2 Oct 2017 09:23:45 +0200 From: Michal Hocko Subject: Re: [PATCH] mm, swap: Make VMA based swap readahead configurable Message-ID: <20171002072345.sd5zcbk4y34hh3mk@dhcp22.suse.cz> References: <20170927074835.37m4dclmew5ecli2@dhcp22.suse.cz> <20170927080432.GA1160@bbox> <20170927083512.dydqlqezh5polggb@dhcp22.suse.cz> <20170927131511.GA338@bgram> <20170927132241.tshup6kcwe5pcxek@dhcp22.suse.cz> <20170927134117.GB338@bgram> <20170927135034.yatxlhvunawzmcar@dhcp22.suse.cz> <20170927141008.GA1278@bgram> <20170927141723.bixcum3fler7q4w5@dhcp22.suse.cz> <87mv5f8wkj.fsf@yhuang-dev.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87mv5f8wkj.fsf@yhuang-dev.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Huang, Ying" Cc: Minchan Kim , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Johannes Weiner , Rik van Riel , Shaohua Li , Hugh Dickins , Fengguang Wu , Tim Chen , Dave Hansen On Thu 28-09-17 09:02:20, Huang, Ying wrote: > Hi, Michal, > > Michal Hocko writes: > > > On Wed 27-09-17 23:10:08, Minchan Kim wrote: > >> On Wed, Sep 27, 2017 at 03:50:34PM +0200, Michal Hocko wrote: > >> > On Wed 27-09-17 22:41:17, Minchan Kim wrote: > >> > > On Wed, Sep 27, 2017 at 03:22:41PM +0200, Michal Hocko wrote: > >> > [...] > >> > > > simply cannot disable swap readahead when page-cluster is 0? > >> > > > >> > > That's was what I want really but Huang want to use two readahead > >> > > algorithms in parallel so he wanted to keep two separated disable > >> > > knobs. > >> > > >> > If it breaks existing and documented behavior then it is a clear > >> > regression and it should be fixed. I do not see why this should be > >> > disputable at all. > >> > >> Indeed but Huang doesn't think so. He has thought it's not a regression. > >> Frankly speaking, I'm really bored of discussing with it. > >> https://marc.info/?l=linux-mm&m=150526413319763&w=2 > > > > Then send a patch explaining why you consider this a regression with > > some numbers backing it and I will happily ack it. > > I still think there may be a performance regression for some users > because of the change of the algorithm and the knobs, and the > performance regression can be resolved via setting the new knob. But I > don't think there will be a functionality regression. Do you agree? I am not sure I understand. One thing is clear though. Your change has introduced a regression as described by Minchan. And that has to be resolved no matter what. You cannot expect users will tweak the system to resolve it or configure their systems in a specific way. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org