From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 15 Nov 2002 13:32:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 15 Nov 2002 13:32:12 -0500 Received: from e33.co.us.ibm.com ([32.97.110.131]:65218 "EHLO e33.co.us.ibm.com") by vger.kernel.org with ESMTP id ; Fri, 15 Nov 2002 13:32:11 -0500 From: Badari Pulavarty Message-Id: <200211151837.gAFIbm610839@eng2.beaverton.ibm.com> Subject: 2.5.47-mm3 IO rate question To: linux-kernel@vger.kernel.org (lkml) Date: Fri, 15 Nov 2002 10:37:48 -0800 (PST) X-Mailer: ELM [version 2.5 PL3] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, I am using 2.5.47-mm3 and qlogic driver qla2x00src-v6.03.00b8. I have 2 qlogic controllers connected to 2 trays (10 disks/tray). I do 256K IO on raw devices using "dd". dd of=/dev/null bs=256k count=2000 if=/dev/raw/raw1 & dd of=/dev/null bs=256k count=2000 if=/dev/raw/raw2 & dd of=/dev/null bs=256k count=2000 if=/dev/raw/raw3 & ... dd of=/dev/null bs=256k count=2000 if=/dev/raw/raw20 & IO throughput changes just by adjusting SG_SEGMENTS (from 32 to 64). I was wondering why such a significant difference. (20MB/sec). I used to get 194-198MB/sec with 2.5.37 (with DIO code sending (fixed) 64K requests - qlogic max_sector=512, SG_SEGMETS=32). Any thoughts ? Thanks, Badari max_sectors = 512 SG_SEGMENTS = 64 [root]# vmstat 5 procs memory swap io system cpu r b w swpd free buff cache si so bi bo in cs us sy id 0 20 0 0 3642680 8832 42836 0 0 194765 15 1762 2183 0 100 0 0 20 0 0 3642680 8836 42836 0 0 194611 3 1761 2122 0 100 0 0 20 0 0 3642680 8840 42836 0 0 194509 3 1774 2150 10 81 8 0 20 0 0 3642680 8844 42836 0 0 194816 3 1762 2132 2 98 0 0 20 0 0 3642680 8848 42836 0 0 194765 3 1764 2177 2 98 0 max_sectors = 512 SG_SEGMENTS = 32 [root]# vmstat 5 procs memory swap io system cpu r b w swpd free buff cache si so bi bo in cs us sy id 0 20 0 0 3652472 7752 34464 0 0 170755 15 2354 3477 2 98 0 0 20 0 0 3652472 7756 34464 0 0 172771 3 2363 3512 2 98 0 0 20 0 0 3652472 7760 34464 0 0 174031 3 2372 3576 0 100 0 0 20 0 0 3652408 7764 34464 0 0 173074 7 2384 3538 10 87 3 0 20 0 0 3652408 7768 34464 0 0 172670 3 2364 3502 2 98 0