Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262408AbVCBTEi (ORCPT ); Wed, 2 Mar 2005 14:04:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262221AbVCBTEi (ORCPT ); Wed, 2 Mar 2005 14:04:38 -0500 Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:53400 "EHLO parcelfarce.linux.theplanet.co.uk") by vger.kernel.org with ESMTP id S262409AbVCBTEd (ORCPT ); Wed, 2 Mar 2005 14:04:33 -0500 Message-ID: <42260E2D.2080407@pobox.com> Date: Wed, 02 Mar 2005 14:04:13 -0500 From: Jeff Garzik User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.3) Gecko/20040922 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Bartlomiej Zolnierkiewicz CC: Tejun Heo , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [patch ide-dev 8/9] make ide_task_ioctl() use REQ_DRIVE_TASKFILE References: <200502271731.29448.bzolnier@elka.pw.edu.pl> <422337A1.4060806@gmail.com> <200502281714.55960.bzolnier@elka.pw.edu.pl> <20050301042116.GA9001@htj.dyndns.org> <58cb370e05030100424d98c85c@mail.gmail.com> <20050301092914.GA14007@htj.dyndns.org> <58cb370e05030101592a46c258@mail.gmail.com> <42255878.7080908@pobox.com> <58cb370e050302020950da588a@mail.gmail.com> In-Reply-To: <58cb370e050302020950da588a@mail.gmail.com> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1422 Lines: 50 Bartlomiej Zolnierkiewicz wrote: > On Wed, 02 Mar 2005 01:08:56 -0500, Jeff Garzik wrote: > >>Bartlomiej Zolnierkiewicz wrote: >> >>>Yes but it seems that you've assumed that ioctl == flagged taskfile >>>and fs/internal == normal taskfile which is _not_ what I aim for. >>> >>>I want fully-flagged taskfile handling like flagged_taskfile() and "hot path" >>>simpler taskfile handling like do_rw_taskfile() (at least for now - we can >>>remove "hot path" later) where both can be used for fs/internal/ioctl requests >>>(depending on the flags). >> >>There is no effective difference in performance between >> >> writeb() >> writeb() >> writeb() >> writeb() >> >>and >> >> if (bit 1) >> writeb() >> if (bit 2) >> writeb() >> if (bit 3) >> writeb() >> if (bit 4) >> writeb() >> >>The cost of a repeated bit test on the same unsigned long is _zero_. >>It's already in L1 cache. The I/Os are slow, and adding bit tests will > > > certainly it is not _zero_ ;-) > > I agree that it is negligible compared to the cost of I/O True :) 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/