Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269429AbUI3S4u (ORCPT ); Thu, 30 Sep 2004 14:56:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269417AbUI3SyI (ORCPT ); Thu, 30 Sep 2004 14:54:08 -0400 Received: from mail.tmr.com ([216.238.38.203]:13063 "EHLO gatekeeper.tmr.com") by vger.kernel.org with ESMTP id S269415AbUI3SxQ (ORCPT ); Thu, 30 Sep 2004 14:53:16 -0400 To: linux-kernel@vger.kernel.org Path: not-for-mail From: Bill Davidsen Newsgroups: mail.linux-kernel Subject: Re: OSDL aio-stress results on latest kernels show buffered random read issue Date: Thu, 30 Sep 2004 14:54:30 -0400 Organization: TMR Associates, Inc Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Trace: gatekeeper.tmr.com 1096569943 6527 192.168.12.100 (30 Sep 2004 18:45:43 GMT) X-Complaints-To: abuse@tmr.com User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20040913 X-Accept-Language: en-us, en In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1521 Lines: 36 Judith Lebzelter wrote: > Hello; > > I am running aio-stress on the most recent kernels and have > found that on linux-2.6.8, 2.6.9-rc2 and 2.6.9-rc2-mm4 the > performance of buffered random reads is poor compared to the > buffered random writes: > > 2.6.8 2.6.9-rc2 2.6.9-rc2-mm4 > -------------------------------------------- > random write 35.66 MB/s 34.80 MB/s 29.89 MB/s > random read 7.69 MB/s 7.50 MB/s 7.68 MB/s > > ** 2CPU hosts with striped Megaraid. 1G RAM. 4G File. > > > This shows up on our 4CPU host as well. (striped AACRAID.4G > RAM. 8G File): > 2.6.9-rc2 2.6.9-rc2-mm4 2.6.9-rc2-mm1 > ------------------------------------------- > random write 31.36 MB/s 18.92 MB/s 18.97 MB/s > random read 11.13 MB/s 9.74 MB/s 11.05 MB/s > > > There seems to be an issue with the reads. Usually, reads > should be at least as fast as writes of the same type. Usually not, since the write goes to cache in most cases while the read must really happen. The 40% slowdown is troubling, though, that's unexpected. -- -bill davidsen (davidsen@tmr.com) "The secret to procrastination is to put things off until the last possible moment - but no longer" -me - 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/