From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753608Ab0ESRFm (ORCPT ); Wed, 19 May 2010 13:05:42 -0400 Received: from mx1.redhat.com ([209.132.183.28]:1217 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752396Ab0ESRFl (ORCPT ); Wed, 19 May 2010 13:05:41 -0400 Message-ID: <4BF41A33.8090309@redhat.com> Date: Wed, 19 May 2010 20:04:51 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4 MIME-Version: 1.0 To: "Michael S. Tsirkin" CC: davem@davemloft.net, Juan Quintela , Rusty Russell , "Paul E. McKenney" , Arnd Bergmann , kvm@vger.kernel.org, virtualization@lists.osdl.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, alex.williamson@redhat.com, amit.shah@redhat.com Subject: Re: [PATCH] vhost-net: utilize PUBLISH_USED_IDX feature References: <20100518011931.GA21918@redhat.com> In-Reply-To: <20100518011931.GA21918@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/18/2010 04:19 AM, Michael S. Tsirkin wrote: > With PUBLISH_USED_IDX, guest tells us which used entries > it has consumed. This can be used to reduce the number > of interrupts: after we write a used entry, if the guest has not yet > consumed the previous entry, or if the guest has already consumed the > new entry, we do not need to interrupt. > This imporves bandwidth by 30% under some workflows. > > Signed-off-by: Michael S. Tsirkin > --- > > Rusty, Dave, this patch depends on the patch > "virtio: put last seen used index into ring itself" > which is currently destined at Rusty's tree. > Rusty, if you are taking that one for 2.6.35, please > take this one as well. > Dave, any objections? > I object: I think the index should have its own cacheline, and that it should be documented before merging. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.