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

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

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'.
 -- Keir




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