Re: [PATCH] per-backing dev unplugging #2

[Jens Axboe]

On Mon, Mar 15 2004, Jeremy Higdon wrote:
> | Hi,
> | 
> | Final version, unless something stupid pops up. Changes:
> | 
> | - Adapt to 2.6.4-mm1
> | - Cleaned up the dm bits, much nicer with the lockless unplugging
> |   (thanks Joe)
> | - md and loop unplugging, stacked devices should unplug their targets.
> |   Otherwise they'll end up waiting for the unplug timer, which sucks.
> | - XFS fixed up, I hope. XFS folks still encouraged to look at this,
> |   looks better this time around though (and works, I tested).
> | - blk_run_* inlined in blkdev.h
> | 
> | Against 2.6.4-mm1 (note you need other attached patch to boot it).
> 
> I got a chance to try this.
> 
> It makes a huge improvement.
> 
> Prior to the last per-cpu patch, I was getting about 75000 to 80000
> IOPS at 100% cpu usage.
> 
> With the per-cpu patch, that went up to 110000 IOPS at 100% CPU.
> 
> With this patch, I'm seeing 200000 IOPS at about 65% CPU usage.
> 
> So it makes a tremendous improvement in I/O scalability, dramatically
> improving performance in small size I/O, high I/O count workloads.
> 
> My tests were on an 8 CPU x 1300 MHz Altix with 64 disks.

That's awesome results, thanks for sharing! And I'm happy to see it's so
worth it, even with the various minor issues we've had with the patch
(hope they are all resolved now).

-- 
Jens Axboe

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