From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [patch ide-dev 8/9] make ide_task_ioctl() use REQ_DRIVE_TASKFILE Date: Wed, 02 Mar 2005 14:04:13 -0500 Message-ID: <42260E2D.2080407@pobox.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit 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 In-Reply-To: <58cb370e050302020950da588a@mail.gmail.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Bartlomiej Zolnierkiewicz Cc: Tejun Heo , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org 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