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

[Nick Piggin]

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.

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