Messages in this thread | | | Date | Wed, 02 Mar 2005 14:04:13 -0500 | From | Jeff Garzik <> | Subject | Re: [patch ide-dev 8/9] make ide_task_ioctl() use REQ_DRIVE_TASKFILE |
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Bartlomiej Zolnierkiewicz wrote: > On Wed, 02 Mar 2005 01:08:56 -0500, Jeff Garzik <jgarzik@pobox.com> 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
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