From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id 053426B0069 for ; Wed, 27 Sep 2017 01:04:08 -0400 (EDT) Received: by mail-pg0-f69.google.com with SMTP id m30so25021184pgn.2 for ; Tue, 26 Sep 2017 22:04:07 -0700 (PDT) Received: from lgeamrelo13.lge.com (LGEAMRELO13.lge.com. [156.147.23.53]) by mx.google.com with ESMTP id 1si6874619plj.222.2017.09.26.22.04.06 for ; Tue, 26 Sep 2017 22:04:06 -0700 (PDT) Date: Wed, 27 Sep 2017 14:04:01 +0900 From: Minchan Kim Subject: Re: [PATCH] mm, swap: Make VMA based swap readahead configurable Message-ID: <20170927050401.GA715@bbox> References: <20170921013310.31348-1-ying.huang@intel.com> <20170926132129.dbtr2mof35x4j4og@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170926132129.dbtr2mof35x4j4og@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 Tue, Sep 26, 2017 at 03:21:29PM +0200, Michal Hocko wrote: > On Thu 21-09-17 09:33:10, Huang, Ying wrote: > > From: Huang Ying > > > > This patch adds a new Kconfig option VMA_SWAP_READAHEAD and wraps VMA > > based swap readahead code inside #ifdef CONFIG_VMA_SWAP_READAHEAD/#endif. > > This is more friendly for tiny kernels. > > How (much)? > > > And as pointed to by Minchan > > Kim, give people who want to disable the swap readahead an opportunity > > to notice the changes to the swap readahead algorithm and the > > corresponding knobs. > > Why would anyone want that? > > Please note that adding new config options make the already complicated > config space even more problematic so there should be a good reason to > add one. Please make sure your justification is clear on why this is > worth the future maintenance and configurability burden. 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 -- 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