From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id A9C0B6B0038 for ; Wed, 27 Sep 2017 21:02:25 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id x78so19850pff.7 for ; Wed, 27 Sep 2017 18:02:25 -0700 (PDT) Received: from mga11.intel.com (mga11.intel.com. [192.55.52.93]) by mx.google.com with ESMTPS id x3si206632pgp.597.2017.09.27.18.02.24 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Sep 2017 18:02:24 -0700 (PDT) From: "Huang\, Ying" Subject: Re: [PATCH] mm, swap: Make VMA based swap readahead configurable References: <20170926132129.dbtr2mof35x4j4og@dhcp22.suse.cz> <20170927050401.GA715@bbox> <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> Date: Thu, 28 Sep 2017 09:02:20 +0800 In-Reply-To: <20170927141723.bixcum3fler7q4w5@dhcp22.suse.cz> (Michal Hocko's message of "Wed, 27 Sep 2017 16:17:23 +0200") Message-ID: <87mv5f8wkj.fsf@yhuang-dev.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ascii Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Minchan Kim , "Huang, Ying" , 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 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? Best Regards, Huang, Ying >> So I passed the decision to Andrew. >> http://lkml.kernel.org/r/<20170913014019.GB29422@bbox> >> >> The config option idea is compromise approach although I don't like it >> and still believe it's simple clear *regression* so 0 page-cluster >> should keep the swap readahead disabled. > > It is not a compromise. The regression is still there for many users > potentially (just consider zram distribution kernel users...). -- 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