Re: [PATCH RFC 3/3] virtio infrastructure: example block driver

[Carsten Otte <cotte-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org>]

Jens Axboe wrote:
> On Fri, Jun 01 2007, Carsten Otte wrote:
>> With regard to compute power needed, almost none. The penalty is 
>> latency, not overhead: A small request may sit on the request queue to 
>> wait for other work to arrive until the queue gets unplugged. This 
>> penality is compensated by the benefit of a good chance that more 
>> requests will be merged during this time period.
>> If we have this method both in host and guest, we have twice the 
>> penalty with no added benefit.
> 
> I don't buy that argument. We can easily expose the unplug delay, so you
> can kill it at what ever level you want. Or you could just do it in the
> driver right now, but that is a bit hackish.
That would be preferable if the device driver can chose the unplug 
delay, or even better it could be (guest)sysfs tuneable.

so long,
Carsten

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