From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754379Ab0EFCbl (ORCPT ); Wed, 5 May 2010 22:31:41 -0400 Received: from ozlabs.org ([203.10.76.45]:52339 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751867Ab0EFCbj (ORCPT ); Wed, 5 May 2010 22:31:39 -0400 From: Rusty Russell To: "Michael S. Tsirkin" Subject: Re: [PATCH RFC] virtio: put last seen used index into ring itself Date: Thu, 6 May 2010 12:01:34 +0930 User-Agent: KMail/1.13.2 (Linux/2.6.32-21-generic; KDE/4.4.2; i686; ; ) Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, qemu-devel@nongnu.org References: <20100505205814.GA7090@redhat.com> In-Reply-To: <20100505205814.GA7090@redhat.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201005061201.35223.rusty@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 6 May 2010 06:28:14 am Michael S. Tsirkin wrote: > Rusty, > this is a simplified form of a patch you posted in the past. > I have a vhost patch that, using this feature, shows external > to host bandwidth grow from 5 to 7 GB/s, by avoiding > an interrupt in the window after previous interrupt > was sent and before interrupts were disabled for the vq. > With vhost under some external to host loads I see > this window being hit about 30% sometimes. Fascinating. So you use this to guess if the guest is still processing? I haven't thought about it hard, but is that racy? Obviously happy to apply this when you finalize it. Thanks! Rusty.