From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932207Ab1GVU7h (ORCPT ); Fri, 22 Jul 2011 16:59:37 -0400 Received: from mga09.intel.com ([134.134.136.24]:30244 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755124Ab1GVU7e (ORCPT ); Fri, 22 Jul 2011 16:59:34 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,249,1309762800"; d="scan'208";a="30927873" Subject: [RFC PATCH 0/2] block: rq_affinity performance fixes To: jaxboe@fusionio.com From: Dan Williams Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Date: Fri, 22 Jul 2011 13:59:33 -0700 Message-ID: <20110722205736.17420.41366.stgit@localhost6.localdomain6> User-Agent: StGit/0.15-7-g9bfb-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jens, Per the "rq_affinity doesn't seem to work?" thread [1]. We found that the default cpu steering that rq_affinity performs is insufficient to keep up with some completion loads. Dave collected the following relative iops measures: pre-patches rq_affinity=0: 1x pre-patches rq_affinity=1: 1x post-patches rq_affinity=1: 1.08x post-patches rq_affinity=2: 1.35x The "adaptive rq_affinity" patch is more of a discussion point than a real fix. However, it shows that even something straightforward and seemingly aggressive does not really come close to the performance of just turning cpu grouping off altogether. The "strict rq_affinity" patch follows the "nomerges" interface precedent of setting 2 to indicate "I really mean it". So, at a minimum consider taking patch 1, and we can leave the search for a better adaptive algorithm as future work. [1]: http://marc.info/?l=linux-kernel&m=131049742925413&w=4 --- Dan Williams (2): block: strict rq_affinity block: adaptive rq_affinity Documentation/block/queue-sysfs.txt | 10 +++++++--- block/blk-core.c | 6 ++---- block/blk-softirq.c | 23 ++++++++++++++++++----- block/blk-sysfs.c | 13 +++++++++---- include/linux/blkdev.h | 3 ++- 5 files changed, 38 insertions(+), 17 deletions(-)