Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752803AbWLREHL (ORCPT ); Sun, 17 Dec 2006 23:07:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752805AbWLREHK (ORCPT ); Sun, 17 Dec 2006 23:07:10 -0500 Received: from wx-out-0506.google.com ([66.249.82.230]:1777 "EHLO wx-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752803AbWLREHJ (ORCPT ); Sun, 17 Dec 2006 23:07:09 -0500 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:mime-version:content-type:content-transfer-encoding:content-disposition; b=sIOwGEC4KIec2a4MVvl4MQguQ3Pt9sK9TktBTM3oIH3NstROqmB7uRQmWtsrQ/Xlj2o8qiRc7frmA4086UMwKG5wp9L8WQIwOpDArIY+nuui7/C3ChtV7/Sch1FfwNZBHgAyd4Jm0s4dOpMXX0vKDnYZft7gs59kVKBXld2vcoQ= Message-ID: <652016d30612172007m58d7a828q378863121ebdc535@mail.gmail.com> Date: Mon, 18 Dec 2006 09:52:08 +0545 From: "Manish Regmi" To: kernelnewbies@nl.linux.org, linux-kernel@vger.kernel.org Subject: Linux disk performance. MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1978 Lines: 60 Hi all, I was working in one application that requires heavy disk writes, I noticed some inconsistencies in the write timing. We are using raw reads to bypass filesystem overhead. Firstly i tried open("/dev/hda",O_RDWR) i.e without O_DIRECT option. I saw that after some writes 1 write took too much time. the results are for writing 128KB data in MIPS 400mhz sequence channel time (in microseconds) 0 1 1675 0 2 1625 0 3 1836 ... 0 16 3398 0 63 1678 1 0 1702 1 1 1845 ..... 3 46 17875 // large value ... 4 13 17142 /// ... 4 44 18711 /// large value Is this behaviour ok? I beleive this is due to deep request queue. But when i used O_DIRECT. I got a little higher write times but it also had such time bumps but at smaller rate. ----------------------------------------- 0 0 3184 0 1 3165 0 2 3126 ... 0 52 10613 // large value 0 60 19004 // large value results similar with O_DIRECT|O_SYNC Can we achieve smooth write times in Linux? I am using 2.6.10 the results are moreover same (i dont mean numerically same but i am getting thiming difference) in both P4 3 GHZ 512MB ram and MIPS. Disk is working in UDMA 5. -- --------------------------------------------------------------- regards Manish Regmi --------------------------------------------------------------- UNIX without a C Compiler is like eating Spaghetti with your mouth sewn shut. It just doesn't make sense. - 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/