Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756812AbZKJP4A (ORCPT ); Tue, 10 Nov 2009 10:56:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756735AbZKJPz7 (ORCPT ); Tue, 10 Nov 2009 10:55:59 -0500 Received: from mx1.redhat.com ([209.132.183.28]:43155 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756731AbZKJPz7 (ORCPT ); Tue, 10 Nov 2009 10:55:59 -0500 From: Jeff Moyer To: Jens Axboe Cc: Corrado Zoccolo , Linux-Kernel , aaronc@gelato.unsw.edu.au Subject: Re: [RFC, PATCH] cfq-iosched: remove redundant queuing detection code References: <200911101454.57522.czoccolo@gmail.com> <20091110151431.GI8742@kernel.dk> <20091110152745.GK8742@kernel.dk> <20091110154809.GL8742@kernel.dk> 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: Tue, 10 Nov 2009 10:55:47 -0500 In-Reply-To: <20091110154809.GL8742@kernel.dk> (Jens Axboe's message of "Tue, 10 Nov 2009 16:48:09 +0100") 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: 961 Lines: 24 Jens Axboe writes: >> Why don't we simply use the value configured via the queue_depth sysfs >> file? > > First of all, that only covers SCSI. We could do that by having the tag > on/off functions set the same flag. But even for such devices, actual > tag depth is dependent upon what other devices are on the controller > (since it's often a shared map) and may not even be statically > detectable in the sense that actual depth is only really seen when the > device returns busy on a queue attempt. > > In most cases it would work fine, but the dynamic detection is more > reliable. The sysfs setting in reality is max setting. OK, thanks for the patient explanation, Jens! 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/