From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935772Ab1JFJSi (ORCPT ); Thu, 6 Oct 2011 05:18:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39460 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932475Ab1JFJSg (ORCPT ); Thu, 6 Oct 2011 05:18:36 -0400 Date: Thu, 6 Oct 2011 11:19:18 -0200 From: "Michael S. Tsirkin" To: Rusty Russell Cc: Christoph Hellwig , Chris Wright , Jens Axboe , Stefan Hajnoczi , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/5] virtio: support unlocked queue kick Message-ID: <20111006131828.GC19023@redhat.com> References: <20111005195403.407628164@bombadil.infradead.org> <20111005195529.964397366@bombadil.infradead.org> <87r52qgaf3.fsf@rustcorp.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87r52qgaf3.fsf@rustcorp.com.au> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 06, 2011 at 12:15:36PM +1030, Rusty Russell wrote: > On Wed, 05 Oct 2011 15:54:05 -0400, Christoph Hellwig wrote: > > Split virtqueue_kick to be able to do the actual notification outside the > > lock protecting the virtqueue. This patch was originally done by > > Stefan Hajnoczi, but I can't find the original one anymore and had to > > recreated it from memory. Pointers to the original or corrections for > > the commit message are welcome. > > An alternative to this is to update the ring on every virtqueue_add_buf. > MST discussed this for virtio_net, and I think it's better in general. > > The only reason that it wasn't written that way originally is that the > barriers make add_buf slightly more expensive. > > Cheers, > Rusty. With event index, I'm not sure that's enough to make the kick lockless anymore. -- MST