From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: [PATCH net-next 8/8] vhost-net: reduce vq polling on tx zerocopy Date: Mon, 29 Oct 2012 17:49:51 +0200 Message-ID: <3e57e2cde71a4270a8fef395c31f5f0e8a130c28.1351524502.git.mst@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Alexander Duyck , Ian Campbell , kvm@vger.kernel.org, "Michael S. Tsirkin" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Eric Dumazet , Andrew Morton , "David S. Miller" Return-path: Content-Disposition: inline In-Reply-To: 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 List-Id: netdev.vger.kernel.org It seems that to avoid deadlocks it is enough to poll vq before we are going to use the last buffer. This should be faster than c70aa540c7a9f67add11ad3161096fb95233aa2e. Signed-off-by: Michael S. Tsirkin --- drivers/vhost/net.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 8e9de79..3967f82 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -197,8 +197,16 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, int status) { struct vhost_ubuf_ref *ubufs = ubuf->ctx; struct vhost_virtqueue *vq = ubufs->vq; - - vhost_poll_queue(&vq->poll); + int cnt = atomic_read(&ubufs->kref.refcount); + + /* + * Trigger polling thread if guest stopped submitting new buffers: + * in this case, the refcount after decrement will eventually reach 1 + * so here it is 2. + * We also trigger polling periodically after each 16 packets. + */ + if (cnt <= 2 || !(cnt % 16)) + vhost_poll_queue(&vq->poll); /* set len to mark this desc buffers done DMA */ vq->heads[ubuf->desc].len = status ? VHOST_DMA_FAILED_LEN : VHOST_DMA_DONE_LEN; -- MST