linux-kernel - Re: [RFC] virtio: use mandatory barriers for remote processor vdevs

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Date:	Wed, 30 Nov 2011 16:50:04 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Ohad Ben-Cohen <ohad@...ery.com>
Cc:	virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [RFC] virtio: use mandatory barriers for remote processor vdevs

On Wed, Nov 30, 2011 at 01:55:53PM +0200, Ohad Ben-Cohen wrote:
> On Tue, Nov 29, 2011 at 5:19 PM, Michael S. Tsirkin <mst@...hat.com> wrote:
> > On Tue, Nov 29, 2011 at 03:57:19PM +0200, Ohad Ben-Cohen wrote:
> >> > Is an extra branch faster or slower than reverting d57ed95?
> >>
> >> Sorry, unfortunately I have no way to measure this, as I don't have
> >> any virtualization/x86 setup. I'm developing on ARM SoCs, where
> >> virtualization hardware is coming, but not here yet.
> >
> > You can try using the micro-benchmark in tools/virtio/.
> 
> Hmm, care to show me exactly what do you mean ?

make headers_install
make -C tools/virtio/
(you'll need an empty stub for tools/virtio/linux/module.h,
 I just sent a patch to add that)
sudo insmod tools/virtio/vhost_test/vhost_test.ko
./tools/virtio/virtio_test

> Though I somewhat suspect that any micro-benchmarking I'll do with my
> random ARM SoC will not have much value to real virtualization/x86
> workloads.
> 
> Thanks,
> Ohad.

Real virtualization/x86 can keep using current smp_XX barriers, right?
We can have some config for your kind of setup.

-- 
MST
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