From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx194.postini.com [74.125.245.194]) by kanga.kvack.org (Postfix) with SMTP id CF4E46B0032 for ; Sat, 27 Apr 2013 06:57:10 -0400 (EDT) Received: by mail-da0-f47.google.com with SMTP id p1so2295559dad.20 for ; Sat, 27 Apr 2013 03:57:10 -0700 (PDT) Date: Sat, 27 Apr 2013 19:14:35 +0800 From: Zheng Liu Subject: Re: [question] call mark_page_accessed() in minor fault Message-ID: <20130427111435.GA6443@gmail.com> References: <20130423122542.GA5638@gmail.com> <5176866A.2060400@openvz.org> <20130423134935.GA10138@gmail.com> <517B79E6.5050204@gmail.com> <20130427075516.GA31442@gmail.com> <517B80DD.7010008@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <517B80DD.7010008@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 03:40:13PM +0800, Simon Jeons wrote: > 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? Multi-threads share one mm_struct and have different task_struct's. Multi-processes have different mm_struct's and task_struct's. Regards, - 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