Re: [Qemu-devel] [regression] dataplane: throughout -40% by commit 580b6b2aa2

[Paolo Bonzini <pbonzini@redhat.com>]

Il 27/06/2014 03:15, Ming Lei ha scritto:
> On Thu, Jun 26, 2014 at 11:57 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> We can implement (advisory) calls like bdrv_plug/bdrv_unplug in order to
>> restore the previous levels of performance.
>
> Yes, that is also what I am thinking, or interfaces like bdrv_queue_io()
> and bdrv_submit_io(), which may match with aio interfaces.

Would you like to try preparing a patch?

>>
>> Note that some fallout of the conversion was expected.  Dataplane told us
>> experimentally what level of performance could be reached, but was a dead
>> end in terms of functionality.  Now Stefan added a whole lot of
>> functionality to dataplane (accounting, throttling, file formats and
>> protocols, thread-pool based I/O, etc.) and we need to bring back any
>> performance we lost in the process.
>
> These features are very good, but looks the conversion is a bit early, :-(

Dataplane is still (and has always been) experimental.  For now, it's a 
playground to get rid of the big QEMU lock in hot paths.  As such, 
performance going up and down is expected.  The good thing is that every 
performance improvement we do now will not be restricted to dataplane, 
it can be applied just as well to any other device.

Paolo