Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264000AbUDQVaF (ORCPT ); Sat, 17 Apr 2004 17:30:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263104AbUDQVaF (ORCPT ); Sat, 17 Apr 2004 17:30:05 -0400 Received: from florence.buici.com ([206.124.142.26]:9088 "HELO florence.buici.com") by vger.kernel.org with SMTP id S264000AbUDQV37 (ORCPT ); Sat, 17 Apr 2004 17:29:59 -0400 Date: Sat, 17 Apr 2004 14:29:58 -0700 From: Marc Singer To: William Lee Irwin III , linux-kernel@vger.kernel.org, akpm@osdl.org, elf@buici.com Subject: Re: vmscan.c heuristic adjustment for smaller systems Message-ID: <20040417212958.GA8722@flea> References: <20040417193855.GP743@holomorphy.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040417193855.GP743@holomorphy.com> User-Agent: Mutt/1.5.5.1+cvs20040105i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1623 Lines: 48 On Sat, Apr 17, 2004 at 12:38:55PM -0700, William Lee Irwin III wrote: > Marc Singer reported an issue where an embedded ARM system performed > poorly due to page replacement potentially prematurely replacing > mapped memory where there was very little mapped pagecache in use to > begin with. > > Marc Singer has results where this is an improvement, and hopefully can > clarify as-needed. Help determining whether this policy change is an > improvement for a broader variety of systems would be appreciated. I have some numbers to clarify the 'improvement'. Setup: ARM922 CPU, 200MHz, 32MiB RAM NFS mounted rootfs, tcp, hard, v3, 4K blocks Test application copies 41MiB file and prints the elapsed time The two scenarios differ only in the setting of /proc/sys/vm/swappiness. swappiness 60 (default) 0 ------------ -------- elapsed time(s) 52.48 52.9 53.13 52.91 53.13 52.87 52.53 53.03 52.35 53.02 mean 52.72 52.94 I'd say that there is no statistically significant difference between these sets of times. However, after I've run the test program, I run the command "ls -l /proc" swappiness 60 (default) 0 ------------ -------- elapsed time(s) 18 1 30 1 33 1 This is the problem. Once RAM fills with IO buffers, the kernel's tendency to evict mapped pages ruins interactive performance. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/