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 <[email protected]>
---
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
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