From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936318AbXGMWf4 (ORCPT ); Fri, 13 Jul 2007 18:35:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758502AbXGMWfo (ORCPT ); Fri, 13 Jul 2007 18:35:44 -0400 Received: from mga01.intel.com ([192.55.52.88]:15289 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758647AbXGMWfn (ORCPT ); Fri, 13 Jul 2007 18:35:43 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.16,538,1175497200"; d="scan'208";a="268069685" From: Dan Williams Subject: [-mm PATCH 0/2] 74% decrease in dispatched writes, stripe-queue take3 To: neilb@suse.de, akpm@linux-foundation.org Cc: raziebe@gmail.com, linux-raid@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 13 Jul 2007 15:35:42 -0700 Message-ID: <20070713223257.25202.74399.stgit@dwillia2-linux.ch.intel.com> User-Agent: StGIT/0.12.1 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Neil, Andrew, The following patches replace the stripe-queue patches currently in -mm. Following your suggestion, Neil, I gathered blktrace data on the number of reads generated by sequential write stimulus. It turns out that reduced pre-reading is not the cause of the performance increase, but rather increased write merging. The data, in patch #1, shows a 74% decrease in the number of dispatched writes. I can only assume that this is the explanation for the 65% throughput improvement, because the occurrence of reads actually increased with these patches applied. This take also fixes observed data corruption while running i/o to a synching array (it was wrong to move the flags parameter from r5dev to r5_queue_dev as things could get out of sync... reverted). Next step is to test reshape under this new queuing model. Regards, Dan