Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754864AbZLBPNS (ORCPT ); Wed, 2 Dec 2009 10:13:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753699AbZLBPNS (ORCPT ); Wed, 2 Dec 2009 10:13:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55222 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752913AbZLBPNR (ORCPT ); Wed, 2 Dec 2009 10:13:17 -0500 From: Jeff Moyer To: Vivek Goyal Cc: Corrado Zoccolo , Linux-Kernel , Jens Axboe Subject: Re: [PATCH 4/4] cfq-iosched: fix corner cases in idling logic References: <200911241449.36336.czoccolo@gmail.com> <4e5e476b0912020614r7352727an62f441e191ae6609@mail.gmail.com> <20091202143808.GB31715@redhat.com> <20091202150234.GC31715@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, 02 Dec 2009 10:13:17 -0500 In-Reply-To: <20091202150234.GC31715@redhat.com> (Vivek Goyal's message of "Wed, 2 Dec 2009 10:02:34 -0500") 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: 1356 Lines: 30 Vivek Goyal writes: > Does it make a big difference. cfq_close_cooperator() does not seem to be > relying on coop flag. It will return us a queue if it thinks there is a > close cooperator. (Irrespective of the fact whether cfqq->new_cfqq has bee > setup yet or not). IIUC, cfqq->new_cfqq will be set in select_queue(). So > in case select_queue() has not run yet, then cfqq->new_cfqq = NULL but we > have a close cooperator. > > But I guess this condition will not hit many a times as select_queue() > happens very frequently on NCQ hardware and the moment select queue finds > close cooperator it will expire the current queue and above check will not > even get a chance to turn. > > So IIUC, if we are here cfqq->new_cfqq is always NULL otherwise select_queue() > by now must have expired us and we will not be here. So either we can > completely remove the check or we can just continue with above check. Wow, I need another cup of coffee for sure. You can just ignore me as I completely misread the code being changed. Sorry for the noise. I'll go make some coffee. 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/