From mboxrd@z Thu Jan 1 00:00:00 1970 From: Herbert Xu Subject: Re: [RFC PATCH 00/17] virtual-bus Date: Thu, 2 Apr 2009 16:52:53 +0800 Message-ID: <20090402085253.GA29932@gondor.apana.org.au> References: <49D46089.5040204@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: ghaskins@novell.com, anthony@codemonkey.ws, andi@firstfloor.org, linux-kernel@vger.kernel.org, agraf@suse.de, pmullaney@novell.com, pmorreale@novell.com, rusty@rustcorp.com.au, netdev@vger.kernel.org, kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from rhun.apana.org.au ([64.62.148.172]:50665 "EHLO arnor.apana.org.au" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753461AbZDBIxM (ORCPT ); Thu, 2 Apr 2009 04:53:12 -0400 Content-Disposition: inline In-Reply-To: <49D46089.5040204@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity 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~} Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt