Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964944AbWLMFdL (ORCPT ); Wed, 13 Dec 2006 00:33:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964943AbWLMFdK (ORCPT ); Wed, 13 Dec 2006 00:33:10 -0500 Received: from mga02.intel.com ([134.134.136.20]:12629 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964942AbWLMFdJ (ORCPT ); Wed, 13 Dec 2006 00:33:09 -0500 X-Greylist: delayed 576 seconds by postgrey-1.27 at vger.kernel.org; Wed, 13 Dec 2006 00:33:09 EST X-ExtLoop1: 1 X-IronPort-AV: i="4.12,160,1165219200"; d="scan'208"; a="173791871:sNHT67998238" From: "Chen, Kenneth W" To: "'AVANTIKA R. MATHUR'" , "Jens Axboe" Cc: "Avantika Mathur" , Subject: RE: cfq performance gap Date: Tue, 12 Dec 2006 21:23:31 -0800 Message-ID: <000001c71e76$d4930e90$bb89030a@amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook 11 Thread-Index: AcceVsEdh/xCMgspS3uWm/7J1Hf9kQAHminA In-Reply-To: <457F583B.9090109@linux.vnet.ibm.com> X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1656 Lines: 37 AVANTIKA R. MATHUR wrote on Tuesday, December 12, 2006 5:33 PM > >> rawio is actually performing sequential reads, but I don't believe it is > >> purely sequential with the multiple processes. > >> I am currently running the test with longer runtimes and will post > >> results once it is complete. > >> I've also attached the rawio source. > >> > > > > It's certainly the slice and idling hurting here. But at the same time, > > I don't really think your test case is very interesting. The test area > > is very small and you have 16 threads trying to read the same thing, > > optimizing for that would be silly as I don't think it has much real > > world relevance. > > Could a database have similar workload to this test? No. Not what I have seen with db workloads exhibits such pattern. There are basically two types of db workloads: one does transaction processing, and I/O pattern are truly random with large stride, both in the context of process and overall I/O seen at device level. A second one is decision making type of db queries. They does large sequential I/O within one process context. This rawio test plows through sequential I/O and modulo each small record over number of threads. So each thread appears to be non-contiguous within its own process context, overall request hitting the device are sequential. I can't see how any application does that kind of I/O pattern. - Ken - 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/