Re: [Qemu-discuss] Using vhost scsi

[Fam Zheng]

On Wed, 07/27 15:17, Michael S. Tsirkin wrote:
> On Wed, Jul 27, 2016 at 09:34:25AM +0100, Stefan Hajnoczi wrote:
> > On Tue, Jul 26, 2016 at 06:35:30PM +0000, Yehuda Yitschak wrote:
> > > Thanks a lot for the detailed answer 
> > > 
> > > I managed to run virtio-scsi and i am benchmarking the performance
> > > 
> > > just curios, does virtio-scsi deliver about the same performance as 
> > > vhost-scsi ? 
> > 
> > Both virtio-scsi and vhost-scsi support many different configurations.
> > If achieving the best performance is critical then you need to benchmark
> > them yourself.
> > 
> > > i was surprised to learn that vhost-scsi isn't widely used.
> > > i thought vhost-scsi should be the favored solution since it should be 
> > > faster but i guess the features you mentioned are also a significant 
> > > factor.
> > 
> > Since virtio-scsi is QEMU userspace code it poses a lower security risk,
> > is easier to update in sync with QEMU itself, and has all the QEMU block
> > layer features.  The performance of vhost-scsi and virtio-scsi should be
> > about the same - they both do the same thing and there's no great
> > advantage to a kernel thread vs userspace thread (they use essentially
> > the same functionality inside the kernel).
> > 
> > Stefan
> 
> That would depend on the workload.  I remember seeing reports of performance
> differences, e.g.:
> 
> http://thread.gmane.org/gmane.comp.emulators.kvm.devel/93601/focus=93777

Not sure whose problem it is but I cannot open this link. Could you paste an
alternative or a subject for google?

Fam