From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id B90E76B0266 for ; Wed, 27 Sep 2017 09:15:25 -0400 (EDT) Received: by mail-pf0-f197.google.com with SMTP id p87so23188266pfj.4 for ; Wed, 27 Sep 2017 06:15:25 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id n12sor4944389pfb.145.2017.09.27.06.15.24 for (Google Transport Security); Wed, 27 Sep 2017 06:15:24 -0700 (PDT) Date: Wed, 27 Sep 2017 22:15:11 +0900 From: Minchan Kim Subject: Re: [PATCH] mm, swap: Make VMA based swap readahead configurable Message-ID: <20170927131511.GA338@bgram> References: <20170921013310.31348-1-ying.huang@intel.com> <20170926132129.dbtr2mof35x4j4og@dhcp22.suse.cz> <20170927050401.GA715@bbox> <20170927074835.37m4dclmew5ecli2@dhcp22.suse.cz> <20170927080432.GA1160@bbox> <20170927083512.dydqlqezh5polggb@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170927083512.dydqlqezh5polggb@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: "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 On Wed, Sep 27, 2017 at 10:35:12AM +0200, Michal Hocko wrote: > On Wed 27-09-17 17:04:32, Minchan Kim wrote: > > On Wed, Sep 27, 2017 at 09:48:35AM +0200, Michal Hocko wrote: > > > On Wed 27-09-17 14:04:01, Minchan Kim wrote: > [...] > > > > The problem is users have disabled swap readahead by echo 0 > /proc/sys/ > > > > vm/page-cluster are regressed by this new interface /sys/kernel/mm/swap/ > > > > vma_ra_max_order. Because for disabling readahead completely, they should > > > > disable vma_ra_max_order as well as page-cluster from now on. > > > > > > > > So, goal of new config to notice new feature to admins so they can be aware > > > > of new konb vma_ra_max_order as well as page-cluster. > > > > I canont think other better idea to preventing such regression. > > > > > > > > http://lkml.kernel.org/r/%3C20170913014019.GB29422@bbox%3E > > > > > > So, how are you going to configure this when you do not know whether > > > zram will be used? In other words what should e.g. distribution set this > > > to? > > > > I have no idea. Unfortunately, it depends on them. If they want to use > > zram as swap, they should fix the script. Surely, I don't like it. > > Instead, I wanted that page-cluster zeroing disables both virtual/pysical > > swap readahead not to break current userspace. However, Huang doesn't > > liek it. > > If you have better idea, please suggest. > > I understand your frustration but config options are not there to bypass > proper design decisions. Why cannot we unconditionally disable all the > read ahead when zram is enabled? It's not a zram specific issue. Every users who have disabled swap readahead via page-cluster will be broken, too. -- 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