Re: [Xen-devel] poor domU VBD performance.

[Andrew Theurer <habanero@xxxxxxxxxx>]

Keir Fraser wrote:

> On 31 Mar 2005, at 16:39, Jens Axboe wrote:
>
> > Not necessarily - either your io rate is not fast enough to sustain a
> > substantial queue depth, in that case you get plugging on basically
> > every io anyways. If on the other hand the io rate is high enough to
> > maintain a queue depth of > 1, then the plugging will never take place
> > because the queue never empties.
> >
> > So all in all, I don't think the temporary work-around will be such a
> > bad idea. I would still rather implement the queue tracking though, it
> > should not be more than a few lines of code.
> I've checked in something along the lines of what you described into 
> both the 2.0-testing and the unstable trees. Looks to have identical 
> performance to the original simple patch, at least for a bulk 'dd'.
I'll do a pull of unstable and see what I get with o_direct, thanks.

-Andrew


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