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Message-ID: <4B30F375.6050103@codemonkey.ws>
Date: Tue, 22 Dec 2009 10:27:33 -0600
From: Anthony Liguori <anthony@...emonkey.ws>
To: Andi Kleen <andi@...stfloor.org>
CC: Gregory Haskins <gregory.haskins@...il.com>,
Avi Kivity <avi@...hat.com>, Ingo Molnar <mingo@...e.hu>,
kvm@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>,
torvalds@...ux-foundation.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
netdev@...r.kernel.org,
"alacrityvm-devel@...ts.sourceforge.net"
<alacrityvm-devel@...ts.sourceforge.net>
Subject: Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33
On 12/22/2009 10:21 AM, Andi Kleen wrote:
>> So far, the only actual technical advantage I've seen is that vbus avoids
>> EOI exits.
>>
> The technical advantage is that it's significantly faster today.
>
There are two separate pieces of code in question. There are front-end
drivers and there are back-end drivers.
Right now, there are only front-end drivers in the kernel today. The
combination of vbus front-end drivers and *kernel* back-end drivers are
faster than the *combination* of virtio front-end drivers and
*userspace* back-end drivers.
vhost-net is our kernel back-end driver. No one has yet established
that the combination of virtio front-end driver and kernel back-end
driver is really significantly slower than vbus.
> Maybe your proposed alternative is as fast, or maybe it's not. Who knows?
>
>
>> We think we understand why vbus does better than the current userspace
>> virtio backend. That's why we're building vhost-net. It's not done yet,
>> but our expectation is that it will do just as well if not better.
>>
> That's the vapourware vs working code disconnect I mentioned. One side has hard
> numbers&working code and the other has expectations. I usually find it sad when the
> vapourware holds up the working code.
>
We're not talking about vaporware. vhost-net exists.
Regards,
Anthony Liguori
> -Andi
>
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