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

[Jens Axboe <axboe@xxxxxxx>]

On Thu, Mar 31 2005, Keir Fraser wrote:
> 
> On 31 Mar 2005, at 08:10, Jens Axboe wrote:
> 
> >Here is a temporary work-around, this should bring you close to 100%
> >performance at the cost of some extra unplugs. Uncompiled.
> 
> Yep, this does the job for me. Thanks! Avoiding the extra unplugs is 
> harder than it sounds as each request in a batch may go to a different 
> request queue. To minimise the number of unplugs per batch we'd need to 
> add code to remember which queues we had used in the current batch, 
> then kick them at the end of the batch. Is there likely to be any 

Or just keep track of the previous queue, if that has changed unplug the
previous queue and update previous queue variable.

> measurable benefit from reducing the number of unplugs?

Probably not, since the plugging happened at the front end as well. So
you should get a nice stream of io in any way.

-- 
Jens Axboe


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