Re: Performance regression in IO scheduler still there

Jan Kara
2009-11-12T17:29:38Z

On Wed 11-11-09 12:43:30, Jeff Moyer wrote:
> Jan Kara <jack@suse.cz> writes:
>
> > Sadly, I don't see the improvement you can see :(. The numbers are the
> > same regardless low_latency set to 0:
> > 2.6.32-rc5 low_latency = 0:
> > 37.39 36.43 36.51 -> 36.776667 0.434920
> > But my testing environment is a plain SATA drive so that probably
> > explains the difference...
>
> I just retested (10 runs for each kernel) on a SATA disk with no NCQ
> support and I could not see a difference. I'll try to dig up a disk
> that support NCQ. Is that what you're using for testing?
I don't think I am. How do I find out?

> 2.6.29 2.6.32-rc6,low_latency=0
> ----------------------------------
> Average: 34.6648 34.4475
> Pop.Std.Dev.: 0.55523 0.21981
Hmm, strange. Miklos Szeredi tried tiobench on his machine and he also
saw the regression. I'll try to think what could make the difference.

Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR