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SubjectRe: [PATCH net-next 8/8] vhost_net: use lockless peeking for skb array during busy polling
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On 2017年03月29日 20:07, Michael S. Tsirkin wrote:
> On Tue, Mar 21, 2017 at 12:04:47PM +0800, Jason Wang wrote:
>> For the socket that exports its skb array, we can use lockless polling
>> to avoid touching spinlock during busy polling.
>>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> ---
>> drivers/vhost/net.c | 7 +++++--
>> 1 file changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
>> index 53f09f2..41153a3 100644
>> --- a/drivers/vhost/net.c
>> +++ b/drivers/vhost/net.c
>> @@ -551,10 +551,13 @@ static int peek_head_len(struct vhost_net_virtqueue *rvq, struct sock *sk)
>> return len;
>> }
>>
>> -static int sk_has_rx_data(struct sock *sk)
>> +static int sk_has_rx_data(struct vhost_net_virtqueue *rvq, struct sock *sk)
>> {
>> struct socket *sock = sk->sk_socket;
>>
>> + if (rvq->rx_array)
>> + return !__skb_array_empty(rvq->rx_array);
>> +
>> if (sock->ops->peek_len)
>> return sock->ops->peek_len(sock);
>>
> I don't see which patch adds __skb_array_empty.

This is not something new, it was introduced by ad69f35d1dc0a
("skb_array: array based FIFO for skbs").

Thanks

>
>> @@ -579,7 +582,7 @@ static int vhost_net_rx_peek_head_len(struct vhost_net *net,
>> endtime = busy_clock() + vq->busyloop_timeout;
>>
>> while (vhost_can_busy_poll(&net->dev, endtime) &&
>> - !sk_has_rx_data(sk) &&
>> + !sk_has_rx_data(rvq, sk) &&
>> vhost_vq_avail_empty(&net->dev, vq))
>> cpu_relax();
>>
>> --
>> 2.7.4

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