From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id B01826B0330 for ; Tue, 12 Sep 2017 04:22:57 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id f84so4111244pfj.0 for ; Tue, 12 Sep 2017 01:22:57 -0700 (PDT) Received: from lgeamrelo12.lge.com (LGEAMRELO12.lge.com. [156.147.23.52]) by mx.google.com with ESMTP id l4si810127pgu.396.2017.09.12.01.22.55 for ; Tue, 12 Sep 2017 01:22:56 -0700 (PDT) Date: Tue, 12 Sep 2017 17:22:53 +0900 From: Minchan Kim Subject: Re: [PATCH 4/5] mm:swap: respect page_cluster for readahead Message-ID: <20170912082253.GA2875@bbox> References: <1505183833-4739-1-git-send-email-minchan@kernel.org> <1505183833-4739-4-git-send-email-minchan@kernel.org> <87vakopk22.fsf@yhuang-dev.intel.com> <20170912062524.GA1950@bbox> <874ls8pga3.fsf@yhuang-dev.intel.com> <20170912065244.GC2068@bbox> <87r2vcnzme.fsf@yhuang-dev.intel.com> <20170912075645.GA2837@bbox> <87mv60nxwa.fsf@yhuang-dev.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87mv60nxwa.fsf@yhuang-dev.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Huang, Ying" Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team , Ilya Dryomov , Sergey Senozhatsky On Tue, Sep 12, 2017 at 04:07:01PM +0800, Huang, Ying wrote: < snip > > >> > My concern is users have been disabled swap readahead by page-cluster would > >> > be regressed. Please take care of them. > >> > >> How about disable VMA based swap readahead if zram used as swap? Like > >> we have done for hard disk? > > > > It could be with SWP_SYNCHRONOUS_IO flag which indicates super-fast, > > no seek cost swap devices if this patchset is merged so VM automatically > > disables readahead. It is in my TODO but it's orthogonal work. > > > > The problem I raised is "Why shouldn't we obey user's decision?", > > not zram sepcific issue. > > > > A user has used SSD as swap devices decided to disable swap readahead > > by some reason(e.g., small memory system). Anyway, it has worked > > via page-cluster for a several years but with vma-based swap devices, > > it doesn't work any more. > > Can they add one more line to their configuration scripts? > > echo 0 > /sys/kernel/mm/swap/vma_ra_max_order We call it as "regression", don't we? -- 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