From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rusty Russell Subject: Re: [PATCH RFC] virtio: put last seen used index into ring itself Date: Thu, 6 May 2010 12:01:34 +0930 Message-ID: <201005061201.35223.rusty__17916.5063811981$1273113125$gmane$org@rustcorp.com.au> References: <20100505205814.GA7090@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20100505205814.GA7090@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S. Tsirkin" Cc: qemu-devel@nongnu.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.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.