From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f71.google.com (mail-it0-f71.google.com [209.85.214.71]) by kanga.kvack.org (Postfix) with ESMTP id 4802B6B0005 for ; Tue, 31 May 2016 21:54:19 -0400 (EDT) Received: by mail-it0-f71.google.com with SMTP id b126so15861349ite.3 for ; Tue, 31 May 2016 18:54:19 -0700 (PDT) Received: from szxga01-in.huawei.com (szxga01-in.huawei.com. [58.251.152.64]) by mx.google.com with ESMTPS id l69si15764436otc.233.2016.05.31.18.54.17 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 31 May 2016 18:54:18 -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> From: zhouxianrong Message-ID: Date: Wed, 1 Jun 2016 09:52:45 +0800 MIME-Version: 1.0 In-Reply-To: <20160531140354.GM26128@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)" >> 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. > 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. On 2016/5/31 22:03, Michal Hocko wrote: > On Tue 31-05-16 13:35:37, zhouxianrong wrote: >> Hey : >> the consideration of this patch is that reusing mapping page >> rather than allocating a new page for page cache when system be >> placed in some states. For lookup pages quickly add a new tag >> PAGECACHE_TAG_REUSE for radix tree which tag the pages that is >> suitable for reusing. >> >> 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? > > [...] > >> How to startup the functional >> 1. the system is under low memory state and there are fs rw operations >> 2. page cache size is get bigger over sysctl limit > > So is this a form of a page cache limit to trigger the reclaim earlier > than on the global memory pressure? > -- 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