From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f71.google.com (mail-pg0-f71.google.com [74.125.83.71]) by kanga.kvack.org (Postfix) with ESMTP id 51E7C6B0033 for ; Thu, 2 Nov 2017 00:22:28 -0400 (EDT) Received: by mail-pg0-f71.google.com with SMTP id u23so4663928pgo.4 for ; Wed, 01 Nov 2017 21:22:28 -0700 (PDT) Received: from lgeamrelo13.lge.com (LGEAMRELO13.lge.com. [156.147.23.53]) by mx.google.com with ESMTP id b75si2705678pfk.343.2017.11.01.21.22.26 for ; Wed, 01 Nov 2017 21:22:26 -0700 (PDT) Date: Thu, 2 Nov 2017 13:22:23 +0900 From: Minchan Kim Subject: Re: =?utf-8?B?562U5aSNOiBbUEFUQ0g=?= =?utf-8?Q?=5D?= mm: extend reuse_swap_page range as much as possible Message-ID: <20171102042223.GA26523@bbox> References: <1509533474-98584-1-git-send-email-zhouxianrong@huawei.com> <87tvyd4fsx.fsf@yhuang-dev.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: zhouxianrong Cc: "Huang, Ying" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "tim.c.chen@linux.intel.com" , "mhocko@suse.com" , "rientjes@google.com" , "mingo@kernel.org" , "vegard.nossum@oracle.com" , "aaron.lu@intel.com" , Zhouxiyu , "Duwei (Device OS)" , fanghua , hutj , Won Ho Park On Thu, Nov 02, 2017 at 02:09:57AM +0000, zhouxianrong wrote: > writes: > > > From: zhouxianrong > > > > origanlly reuse_swap_page requires that the sum of page's mapcount and > > swapcount less than or equal to one. > > in this case we can reuse this page and avoid COW currently. > > > > now reuse_swap_page requires only that page's mapcount less than or > > equal to one and the page is not dirty in swap cache. in this case we > > do not care its swap count. > > > > the page without dirty in swap cache means that it has been written to > > swap device successfully for reclaim before and then read again on a > > swap fault. in this case the page can be reused even though its swap > > count is greater than one and postpone the COW on other successive > > accesses to the swap cache page later rather than now. > > > > i did this patch test in kernel 4.4.23 with arm64 and none huge > > memory. it work fine. > > Why do you need this? You saved copying one page from memory to memory > (COW) now, at the cost of reading a page from disk to memory later? > > yes, accessing later does not always happen, there is probability for it, so postpone COW now. So, it's trade-off. It means we need some number with some scenarios to prove it's better than as-is. It would help to drive reviewers/maintainer. Thanks. -- 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