From mboxrd@z Thu Jan 1 00:00:00 1970 From: Qin Chuanyu Subject: [PATCH] vhost: poll vhost_net only when tx notification is enabled Date: Wed, 26 Feb 2014 17:20:09 +0800 Message-ID: <530DB1C9.2060106@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Cc: To: , "Michael S. Tsirkin" , Jason Wang , , KVM list Return-path: Sender: netdev-owner@vger.kernel.org List-Id: kvm.vger.kernel.org guest kick host base on avail_ring flags value and get perfermance improved, vhost_zerocopy_callback could do the same thing. As virtqueue_enable_cb need one more check after modifying the value of avail_ring flags, vhost also need do the same thing after vhost_enable_notify. test result list as below: guest and host: suse11sp3, netperf, intel CPU 2.4GHz +------+----------+--------+----------+--------+--------+---------+ | | old | new | +------+----------+--------+----------+--------+--------+---------+ | UDP | Gbit/s | PPS |CPU idle% | Gbit/s | PPS |CPU idle%| | 256 | 0.74805 | 321309 | 87.16 | 0.77933| 334743 | 90.71 | | 512 | 1.42 | 328475 | 87.03 | 1.44 | 333550 | 90.43 | | 1024 | 2.79 | 334426 | 89.09 | 2.81 | 336986 | 89.55 | | 1460 | 3.71 | 316215 | 87.53 | 4.02 | 342325 | 89.58 | +------+----------+--------+----------+--------+--------+---------+ Signed-off-by: Chuanyu Qin --- drivers/vhost/net.c | 13 ++++++++++++- 1 files changed, 12 insertions(+), 1 deletions(-) diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index a0fa5de..a90f51b 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -315,6 +315,10 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success) VHOST_DMA_DONE_LEN : VHOST_DMA_FAILED_LEN; cnt = vhost_net_ubuf_put(ubufs); + /* make sure len has been updated because handle_tx would use it + * and used_flags should also been checked. + */ + smp_mb(); /* * Trigger polling thread if guest stopped submitting new buffers: * in this case, the refcount after decrement will eventually reach 1. @@ -322,7 +326,8 @@ static void vhost_zerocopy_callback(struct ubuf_info *ubuf, bool success) * (the value 16 here is more or less arbitrary, it's tuned to trigger * less than 10% of times). */ - if (cnt <= 1 || !(cnt % 16)) + if ((!(vq->used_flags & VRING_USED_F_NO_NOTIFY)) + && (cnt <= 1 || !(cnt % 16))) vhost_poll_queue(&vq->poll); rcu_read_unlock_bh(); @@ -386,6 +391,12 @@ static void handle_tx(struct vhost_net *net) vhost_disable_notify(&net->dev, vq); continue; } + /* there might skb been freed between last + * vhost_zerocopy_signal_used and vhost_enable_notify, + * so one more check is needed. + */ + if (zcopy) + vhost_zerocopy_signal_used(net, vq); break; } if (in) { -- 1.7.3.1.msysgit.0