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?
>
> 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?
> + 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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