On 2014/2/25 15:38, Jason Wang wrote:
On 02/25/2014 02:55 PM, Qin Chuanyu wrote:
guest kick vhost base on vring flag status and get perfermance improved,
vhost_zerocopy_callback could do this in the same way, as
virtqueue_enable_cb need one more check after change the status of
avail_ring flags, vhost also do the same thing after vhost_enable_notify
test result list as below:
guest and host: suse11sp3, netperf, intel 2.4GHz
+-------+----------+---------+----------+---------+
| | old | new |
+-------+----------+---------+----------+---------+
| UDP | Gbit/s | PPS | Gbit/s | PPS |
| 256 | 0.74805 | 321309 | 0.77933 | 334743 |
| 512 | 1.42 | 328475 | 1.44 | 333550 |
| 1024 | 2.79 | 334426 | 2.81 | 336986 |
| 1460 | 3.71 | 316215 | 4.02 | 342325 |
+-------+----------+---------+----------+---------+
Looks good, do you have cpu utilization number?
+------+----------+--------+----------+--------+--------+---------+
| | 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 |
+------+----------+--------+----------+--------+--------+---------+
after change, less cpu has been used.
Signed-off-by: Chuanyu Qin <qinchuanyu@xxxxxxxxxx>
---
drivers/vhost/net.c | 10 +++++++++-
1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index a0fa5de..9bc0a15 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -322,7 +322,9 @@ 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))
+ smp_rmb();
Better add a comment to explain why this is needed.
Looks like what you need is a smp_mb() here to make sure the len is
updated before testing vq->used_flags?
I wanner make sure the used_flags is updated, is smp_rmb() enough?
or a smp_mb() is needed?
+ if ((!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
+ && (cnt <= 1 || !(cnt % 16)))
vhost_poll_queue(&vq->poll);
rcu_read_unlock_bh();
@@ -386,6 +388,12 @@ 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) {
.
--
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