From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: [V2 PATCH 7/9] vhost_net: re-poll only on EAGAIN or ENOBUFS Date: Wed, 02 May 2012 11:42:32 +0800 Message-ID: <20120502034232.11782.46122.stgit@amd-6168-8-1.englab.nay.redhat.com> References: <20120502033901.11782.13157.stgit@amd-6168-8-1.englab.nay.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit To: eric.dumazet@gmail.com, mst@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, ebiederm@xmission.com, davem@davemloft.net Return-path: Received: from mx1.redhat.com ([209.132.183.28]:6371 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758594Ab2EBDrs (ORCPT ); Tue, 1 May 2012 23:47:48 -0400 In-Reply-To: <20120502033901.11782.13157.stgit@amd-6168-8-1.englab.nay.redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: Currently, we restart tx polling unconditionally when sendmsg() fails. This would cause unnecessary wakeups of vhost wokers and waste cpu utlization when evil userspace(guest driver) is able to hit EFAULT or EINVAL. The polling is only needed when the socket send buffer were exceeded or not enough memory. So fix this by restarting polling only when sendmsg() returns EAGAIN/ENOBUFS. Signed-off-by: Jason Wang --- drivers/vhost/net.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index ffdc0d8..62828aa 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -257,7 +257,8 @@ static void handle_tx(struct vhost_net *net) UIO_MAXIOV; } vhost_discard_vq_desc(vq, 1); - tx_poll_start(net, sock); + if (err == -EAGAIN || err == -ENOBUFS) + tx_poll_start(net, sock); break; } if (err != len)