From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f70.google.com (mail-pa0-f70.google.com [209.85.220.70]) by kanga.kvack.org (Postfix) with ESMTP id EA84D6B0005 for ; Wed, 1 Jun 2016 05:36:27 -0400 (EDT) Received: by mail-pa0-f70.google.com with SMTP id di3so9357994pab.0 for ; Wed, 01 Jun 2016 02:36:27 -0700 (PDT) Received: from szxga01-in.huawei.com ([58.251.152.64]) by mx.google.com with ESMTPS id qz13si5912115pac.50.2016.06.01.02.36.25 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 01 Jun 2016 02:36:27 -0700 (PDT) Subject: =?UTF-8?Q?Re:_=e7=ad=94=e5=a4=8d:_[PATCH]_reusing_of_mapping_page_s?= =?UTF-8?Q?upplies_a_way_for_file_page_allocation_under_low_memory_due_to_pa?= =?UTF-8?Q?gecache_over_size_and_is_controlled_by_sysctl_parameters._it_is_u?= =?UTF-8?Q?sed_only_for_rw_page_allocation_rather_than_fault_or_readahead_al?= =?UTF-8?Q?location._it_is_like...?= References: <1464685702-100211-1-git-send-email-zhouxianrong@huawei.com> <20160531093631.GH26128@dhcp22.suse.cz> <20160531140354.GM26128@dhcp22.suse.cz> <20160601081820.GG26601@dhcp22.suse.cz> From: zhouxianrong Message-ID: Date: Wed, 1 Jun 2016 17:28:34 +0800 MIME-Version: 1.0 In-Reply-To: <20160601081820.GG26601@dhcp22.suse.cz> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: "viro@zeniv.linux.org.uk" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , Zhouxiyu , "wanghaijun (E)" , "Yuchao (T)" > Why would you want to reuse a page about which you have no idea about > its age compared to the LRU pages which would be mostly clean as well? > I mean this needs a deep justification! > pages only dirtied by rw syscall can be reused pages dirtied by fault due to page_mkwrite or bdi-dirty-account now does not be reused On 2016/6/1 16:18, Michal Hocko wrote: > On Wed 01-06-16 09:52:45, zhouxianrong wrote: >>>> A page suitable for reusing within mapping is >>>> 1. clean >>>> 2. map count is zero >>>> 3. whose mapping is evictable >>> >>> Those pages are trivially reclaimable so why should we tag them in a >>> special way? >> yes, those pages can be reclaimed by reclaim procedure. i think in low memory >> case for a process that doing file rw directly-reusing-mapping-page may be >> a choice than alloc_page just like directly reclaim. alloc_page could failed return >> due to gfp and watermark in low memory. for reusing-mapping-page procedure quickly >> select a page that is be reused so introduce a tag for this purpose. > > Why would you want to reuse a page about which you have no idea about > its age compared to the LRU pages which would be mostly clean as well? > I mean this needs a deep justification! > >>> So is this a form of a page cache limit to trigger the reclaim earlier >>> than on the global memory pressure? > >> my thinking is that page cache limit trigger reuse-mapping-page. the >> limit is earlier than on the global memory pressure. >> reuse-mapping-page can suppress increment of page cache size and big page cache size >> is one reason of low memory and fragment. > > But why would you want to limit the amount of the page cache in the > first place when it should be trivially reclaimable most of the time? > -- 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