From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx166.postini.com [74.125.245.166]) by kanga.kvack.org (Postfix) with SMTP id B915B6B0032 for ; Sat, 27 Apr 2013 03:40:23 -0400 (EDT) Received: by mail-pa0-f53.google.com with SMTP id bh4so2860422pad.40 for ; Sat, 27 Apr 2013 00:40:22 -0700 (PDT) Message-ID: <517B80DD.7010008@gmail.com> Date: Sat, 27 Apr 2013 15:40:13 +0800 From: Simon Jeons MIME-Version: 1.0 Subject: Re: [question] call mark_page_accessed() in minor fault References: <20130423122542.GA5638@gmail.com> <5176866A.2060400@openvz.org> <20130423134935.GA10138@gmail.com> <517B79E6.5050204@gmail.com> <20130427075516.GA31442@gmail.com> In-Reply-To: <20130427075516.GA31442@gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Zheng Liu Cc: Konstantin Khlebnikov , linux-mm@kvack.org, muming.wq@taobao.com Hi Zheng, On 04/27/2013 03:55 PM, Zheng Liu wrote: > On Sat, Apr 27, 2013 at 03:10:30PM +0800, Simon Jeons wrote: >> Hi Zheng, >> On 04/23/2013 09:49 PM, Zheng Liu wrote: >>> Hi Konstantin, >>> >>> On Tue, Apr 23, 2013 at 05:02:34PM +0400, Konstantin Khlebnikov wrote: >>>> Zheng Liu wrote: >>>>> Hi all, >>>>> >>>>> Recently we meet a performance regression about mmaped page. When we upgrade >>>>> our product system from 2.6.18 kernel to a latest kernel, such as 2.6.32 kernel, >>>>> we will find that mmaped pages are reclaimed very quickly. We found that when >>>>> we hit a minor fault mark_page_accessed() is called in 2.6.18 kernel, but in >>>>> 2.6.32 kernel we don't call mark_page_accesed(). This means that mmaped pages >>>>> in 2.6.18 kernel are activated and moved into active list. While in 2.6.32 >>>>> kernel mmaped pages are still kept in inactive list. >>>>> >>>>> So my question is why we call mark_page_accessed() in 2.6.18 kernel, but don't >>>>> call it in 2.6.32 kernel. Has any reason here? >>>> Behavior was changed in commit >>>> v2.6.28-6130-gbf3f3bc "mm: don't mark_page_accessed in fault path" >>> Thanks for pointing it out. >>> >>>> Please see also commits >>>> v3.2-4876-g34dbc67 "vmscan: promote shared file mapped pages" and >>> Yes, I will give it try. If I understand correctly, this commit is >>> useful for multi-processes program that access a shared mmaped page, >>> but that could not be useful for us because our program is multi-thread. >> What's the difference behavior between multi-processes and >> multi-thread in this case? > Hi Simon, > > Sorry, I am not a MM expert. IIUC, if we have two processes, this > mmaped page will be moved into active list. But if we only have two > threads, reference_ptes == 1, and this mmaped page won't be moved into > active list. Finally this page could be evicted. Am I missing > something? Multi-threads will have same mm_struct and task_struct? > > Thanks, > - Zheng -- 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