Re: poor domU VBD performance.

[Andrew Theurer <habanero@us.ibm.com>]

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