Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269056AbUIHPPo (ORCPT ); Wed, 8 Sep 2004 11:15:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269066AbUIHPPo (ORCPT ); Wed, 8 Sep 2004 11:15:44 -0400 Received: from omx2-ext.sgi.com ([192.48.171.19]:35016 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S269056AbUIHPPc (ORCPT ); Wed, 8 Sep 2004 11:15:32 -0400 Message-ID: <413F2317.4050401@sgi.com> Date: Wed, 08 Sep 2004 10:19:51 -0500 From: Ray Bryant User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Marcelo Tosatti CC: Con Kolivas , Andrew Morton , linux-kernel@vger.kernel.org, linux-mm@kvack.org, riel@redhat.com, piggin@cyberone.com.au, mbligh@aracnet.com Subject: Re: swapping and the value of /proc/sys/vm/swappiness References: <413CB661.6030303@sgi.com> <20040906162740.54a5d6c9.akpm@osdl.org> <20040907000304.GA8083@logos.cnet> <20040907212051.GC3492@logos.cnet> In-Reply-To: <20040907212051.GC3492@logos.cnet> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1994 Lines: 46 Marcelo Tosatti wrote: > Ray, I see the additional swapouts increase the dd performance for your particular testcase: > > on 2.6.6: > Total I/O Avg Swap min max pg cache min max > ----------- --------- ------- ------ --------- ------- ------- > 0 242.47 MB/s 0 MB ( 0, 0) 3195 MB ( 3138, 3266) > 20 256.06 MB/s 0 MB ( 0, 0) 3170 MB ( 3074, 3234) > 40 267.29 MB/s 0 MB ( 0, 0) 3189 MB ( 3137, 3234) > 60 289.43 MB/s 666 MB ( 72, 1680) 3847 MB ( 3296, 4817) <---------- > > So for this one testcase it is being beneficial. > True enough, but the general trend is that increasing swapping decreases data rate. This is even more true for the real applications that we are modelling with this simple benchmark. In thosec cases, the user has a lot of mapped data that they then write out using buffered I/O. If the mapped data gets swapped out, then it may have to be swapped back in to be written out to the file system. It would be faster to keep the mapped data from being swapped out at all provided that there is enough page cache space to keep the devices running at full speed. (And yes, we've suggested that they mmap() the data files -- but sometimes this is an ISV's code that it causing the problem and we can't necessarily get them to update their codes to use the API's we want.) -- Best Regards, Ray ----------------------------------------------- Ray Bryant 512-453-9679 (work) 512-507-7807 (cell) raybry@sgi.com raybry@austin.rr.com The box said: "Requires Windows 98 or better", so I installed Linux. ----------------------------------------------- - 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/