From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx176.postini.com [74.125.245.176]) by kanga.kvack.org (Postfix) with SMTP id D2F126B0033 for ; Tue, 23 Apr 2013 09:32:13 -0400 (EDT) Received: by mail-da0-f47.google.com with SMTP id p1so344456dad.20 for ; Tue, 23 Apr 2013 06:32:13 -0700 (PDT) Date: Tue, 23 Apr 2013 21:49:35 +0800 From: Zheng Liu Subject: Re: [question] call mark_page_accessed() in minor fault Message-ID: <20130423134935.GA10138@gmail.com> References: <20130423122542.GA5638@gmail.com> <5176866A.2060400@openvz.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5176866A.2060400@openvz.org> Sender: owner-linux-mm@kvack.org List-ID: To: Konstantin Khlebnikov Cc: linux-mm@kvack.org, muming.wq@taobao.com 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. > v3.2-4877-gc909e99 "vmscan: activate executable pages after first usage". We have backported this patch, but it is useless. This commit only tries to activate a executable page, but our mmaped pages aren't with this flag. Additional question is that currently mmaped page is reclaimed too quickly. I think maybe we need to adjust our page reclaim strategy to balance number of pages between mmaped page and file page cache. Now every time we access a page using read(2)/write(2), this page will be touched. But after first time we touch a mmaped page, we never touch it again except that this page is evicted. 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