From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: [PATCH 0/3] virtio: don't poll masked vectors with irqfd Date: Tue, 18 Dec 2012 14:39:11 +0200 Message-ID: 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]:9165 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754484Ab2LRMgH (ORCPT ); Tue, 18 Dec 2012 07:36:07 -0500 Content-Disposition: inline Sender: kvm-owner@vger.kernel.org List-ID: 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. Michael S. Tsirkin (3): msi: add API to get notified about pending bit poll msix: expose access to masked/pending state virtio-pci: don't poll masked vectors hw/pci/msix.c | 19 +++++++++++++++---- hw/pci/msix.h | 6 +++++- hw/pci/pci.h | 4 ++++ hw/vfio_pci.c | 2 +- hw/virtio-pci.c | 53 +++++++++++++++++++++++++++++++++++++++++------------ 5 files changed, 66 insertions(+), 18 deletions(-) -- MST