Re: [patch ide-dev 8/9] make ide_task_ioctl() use REQ_DRIVE_TASKFILE

[Jeff Garzik]

Bartlomiej Zolnierkiewicz wrote:
> On Wed, 02 Mar 2005 01:08:56 -0500, Jeff Garzik <jgarzik@xxxxxxxxx> 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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