From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753585Ab0ESQQI (ORCPT ); Wed, 19 May 2010 12:16:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19700 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753742Ab0ESQQE (ORCPT ); Wed, 19 May 2010 12:16:04 -0400 Message-ID: <4BF40E8D.7020409@redhat.com> Date: Wed, 19 May 2010 19:15:09 +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: [PATCHv2] vhost-net: utilize PUBLISH_USED_IDX feature References: <20100518022105.GA23129@redhat.com> <4BF2D2A7.8030803@redhat.com> In-Reply-To: <4BF2D2A7.8030803@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 08:47 PM, Avi Kivity wrote: > On 05/18/2010 05:21 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. > > Seems to be missing the cacheline alignment. > > Rusty's clarification did not satisfy me, I think it's needed. > Oh, and this should definitely follow the patch to the virtio spec, not precede it. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic.