From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 0/3] virtio: don't poll masked vectors with irqfd Date: Tue, 18 Dec 2012 14:41:10 +0200 Message-ID: <20121218124110.GA25463@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: qemu-devel@nongnu.org, Marcelo Tosatti , Jan Kiszka , Peter Maydell , kvm@vger.kernel.org To: Asias He Return-path: Received: from mx1.redhat.com ([209.132.183.28]:62442 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752924Ab2LRMiE (ORCPT ); Tue, 18 Dec 2012 07:38:04 -0500 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Dec 18, 2012 at 02:20:20PM +0200, Michael S. Tsirkin wrote: > At the moment when vector is masked virtio will poll it > in userspace, even if it is handled by irqfd. > This is done in order to update pending bits, but > it's not really required until someone reads the pending bits. > On the other hand this read results in extra io thread wakeups. > > As we only implement the pending bits as a compatibility > feature (read - real drivers don't use it), we can defer > the irqfd poll until the read actually happens. > > This does not seem to affect vhost-net speed > in simple benchmarks but could help block: both > vhost-blk and dataplane when using irqfd, > and I also think this is cleaner than enabling/disabling > notifiers all the time. > > This will also be the basis for future optimizations. Note: this is on top of the typesafe bindings patch v3 I sent previously. You can get the whole bundle from: git://git.kernel.org/pub/scm/virt/kvm/mst/qemu.git pci -- MST