From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx170.postini.com [74.125.245.170]) by kanga.kvack.org (Postfix) with SMTP id B19386B0032 for ; Sat, 27 Apr 2013 03:37:51 -0400 (EDT) Received: by mail-pd0-f171.google.com with SMTP id t10so20560pdi.16 for ; Sat, 27 Apr 2013 00:37:51 -0700 (PDT) Date: Sat, 27 Apr 2013 15:55:16 +0800 From: Zheng Liu Subject: Re: [question] call mark_page_accessed() in minor fault Message-ID: <20130427075516.GA31442@gmail.com> References: <20130423122542.GA5638@gmail.com> <5176866A.2060400@openvz.org> <20130423134935.GA10138@gmail.com> <517B79E6.5050204@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <517B79E6.5050204@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Simon Jeons Cc: Konstantin Khlebnikov , linux-mm@kvack.org, muming.wq@taobao.com 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? 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