From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 843466B004F for ; Sat, 16 May 2009 04:53:51 -0400 (EDT) Date: Sat, 16 May 2009 16:54:16 +0800 From: Wu Fengguang Subject: Re: [PATCH -mm] vmscan: protect a fraction of file backed mapped pages from reclaim Message-ID: <20090516085416.GA10221@localhost> References: <20090512120002.D616.A69D9226@jp.fujitsu.com> <20090513084306.5874.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org To: Christoph Lameter Cc: KOSAKI Motohiro , Andrew Morton , "hannes@cmpxchg.org" , "peterz@infradead.org" , "riel@redhat.com" , "linux-kernel@vger.kernel.org" , "tytso@mit.edu" , "linux-mm@kvack.org" , "elladan@eskimo.com" , "npiggin@suse.de" , "minchan.kim@gmail.com" List-ID: Hi Christoph, On Fri, May 15, 2009 at 04:14:31AM +0800, Christoph Lameter wrote: > On Wed, 13 May 2009, KOSAKI Motohiro wrote: > > > > All these expiration modifications do not take into account that a desktop > > > may sit idle for hours while some other things run in the background (like > > > backups at night or updatedb and other maintenance things). This still > > > means that the desktop will be usuable in the morning. > > > > Have you seen this phenomenom? > > I always use linux desktop for development. but I haven't seen it. > > perhaps I have no luck. I really want to know reproduce way. > > > > Please let me know reproduce way. > > Run a backup (or rsync) over a few hundred GB. Simple experiments show that rsync is use-once workload: 1) fresh run(full backup): the source file pages in the logo/ dir are cached and referenced *once*: rsync -a logo localhost:/tmp/ 2) second run(incremental backup): only the updated files are read and read only once: rsync -a logo localhost:/tmp/ > > > The percentage of file backed pages protected is set via > > > /proc/sys/vm/file_mapped_ratio. This defaults to 20%. > > > > Why do you think typical mapped ratio is less than 20% on desktop machine? > > Observation of the typical mapped size of Firefox under KDE. Since the explicit PROT_EXEC targeted mmap page protection plus Rik's use-once patch works just OK for rsync - a typical backup scenario, and it works without an extra sysctl tunable, I tend to continue pushing the PROT_EXEC approach :-) Thanks, Fengguang > > key point is access-once vs access-many. > > Nothing against it if it works. -- 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