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

[Jeff Garzik <jgarzik@pobox.com>]

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