Re: [PATCH] tun: use netif_receive_skb instead of netif_rx_ni

Qin Chuanyu
2014-02-12T06:46:16Z

On 2014/2/12 13:28, Jason Wang wrote:

> A question: without NAPI weight, could this starve other net devices?
tap xmit skb use thread context，the poll func of physical nic driver
could be called in softirq context without change.

I had test it by binding vhost thread and physic nic interrupt on the
same vcpu, use netperf xmit udp, test model is VM1-Host1-Host2.

if only VM1 xmit skb, the top show as below :
Cpu1 :0.0%us, 95.0%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 5.0%si, 0.0%st

then use host2 xmit skb to VM1, the top show as below :
Cpu1 :0.0%us, 41.0%sy, 0.0%ni, 0.0%id, 0.0%wa, 0.0%hi, 59.0%si, 0.0%st

so I think there is no problem with this change.

>> drivers/net/tun.c | 4 +++-
>> 1 files changed, 3 insertions(+), 1 deletions(-)
>>
>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
>> index 44c4db8..90b4e58 100644
>> --- a/drivers/net/tun.c
>> +++ b/drivers/net/tun.c
>> @@ -1184,7 +1184,9 @@ static ssize_t tun_get_user(struct tun_struct
>> *tun, struct tun_file *tfile,
>> skb_probe_transport_header(skb, 0);
>>
>> rxhash = skb_get_hash(skb);
>> - netif_rx_ni(skb);
>> + rcu_read_lock_bh();
>> + netif_receive_skb(skb);
>> + rcu_read_unlock_bh();
>>
>> tun->dev->stats.rx_packets++;
>> tun->dev->stats.rx_bytes += len;
>
>
> .
>