Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752583Ab0GUUdW (ORCPT ); Wed, 21 Jul 2010 16:33:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:8238 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752123Ab0GUUdT (ORCPT ); Wed, 21 Jul 2010 16:33:19 -0400 From: Jeff Moyer To: Vivek Goyal Cc: linux-kernel@vger.kernel.org, axboe@kernel.dk, nauman@google.com, dpshah@google.com, guijianfeng@cn.fujitsu.com, czoccolo@gmail.com Subject: Re: [PATCH 1/3] cfq-iosched: Implment IOPS mode References: <1279739181-24482-1-git-send-email-vgoyal@redhat.com> <1279739181-24482-2-git-send-email-vgoyal@redhat.com> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Wed, 21 Jul 2010 16:33:04 -0400 In-Reply-To: <1279739181-24482-2-git-send-email-vgoyal@redhat.com> (Vivek Goyal's message of "Wed, 21 Jul 2010 15:06:19 -0400") Message-ID: User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1502 Lines: 30 Vivek Goyal writes: > o Implement another CFQ mode where we charge queue/group in terms of number > of requests dispatched instead of measuring the time. Measuring in terms > of time is not possible when we are driving deeper queue depths and there > are requests from multiple cfq queues in the request queue. > > o This mode currently gets activated if one sets slice_idle=0 and associated > disk supports NCQ. Again the idea is that on an NCQ disk with idling disabled > most of the queues will dispatch 1 or more requests and then cfq queue > expiry happens and we don't have a way to measure time. So start providing > fairness in terms of IOPS. > > o Currently this primarily is beneficial with cfq group scheduling where one > can disable slice idling so that we don't idle on queue and drive deeper > request queue deptsh (achieving better throughput), at the same time group > idle is enabled so one should get service differentiation among groups. I like that this is more isolated now. I'm slowly warming up to it. I have one question--just a curiosity, really. What do you see now for the reported sl_used in blktrace when slice_idle is zero and the hardware supports command queueing? Cheers, Jeff -- 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/