Re: [patch] use cheaper elv_queue_empty when unplug a device

Jens Axboe
2005-04-08T09:46:07Z

On Wed, Mar 30 2005, Nick Piggin wrote:
> Nick Piggin wrote:
> >Jens Axboe wrote:
> >
> >>Looks good, I've been toying with something very similar for a long time
> >>myself.
> >>
> >
> >Here is another thing I just noticed that should further reduce the
> >locking by at least 1, sometimes 2 lock/unlock pairs per request.
> >At the cost of uglifying the code somewhat. Although it is pretty
> >nicely contained, so Jens you might consider it acceptable as is,
> >or we could investigate how to make it nicer if Kenneth reports some
> >improvement.
> >
> >Note, this isn't runtime tested - it could easily have a bug.
> >
>
> OK - I have booted this on a 4-way SMP with SCSI disks, and done
> some IO tests, and no hangs.
>
> So Kenneth if you could look into this one as well, to see if
> it is worthwhile, that would be great.

For that to work, you have to change the get_io_context() allocation to
be GFP_ATOMIC.

--
Jens Axboe