netdev - Re: [RFC PATCH 00/17] virtual-bus

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Date:	Thu, 2 Apr 2009 16:52:53 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Avi Kivity <avi@...hat.com>
Cc:	ghaskins@...ell.com, anthony@...emonkey.ws, andi@...stfloor.org,
	linux-kernel@...r.kernel.org, agraf@...e.de, pmullaney@...ell.com,
	pmorreale@...ell.com, rusty@...tcorp.com.au,
	netdev@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [RFC PATCH 00/17] virtual-bus

Avi Kivity <avi@...hat.com> wrote:
>
> virtio is already non-kvm-specific (lguest uses it) and non-pci-specific 
> (s390 uses it).

I think Greg's work shows that putting the backend in the kernel
can dramatically reduce the cost of a single guest->host transaction.
I'm sure the same thing would work for virtio too.

> If you have a good exit mitigation scheme you can cut exits by a factor 
> of 100; so the userspace exit costs are cut by the same factor.  If you 
> have good copyless networking APIs you can cut the cost of copies to 
> zero (well, to the cost of get_user_pages_fast(), but a kernel solution 
> needs that too).

Given the choice of having to mitigate or not having the problem
in the first place, guess what I would prefer :)

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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