On 2014/1/28 16:34, Michael S. Tsirkin wrote:
On Tue, Jan 28, 2014 at 04:14:12PM +0800, Qin Chuanyu wrote:
according perf test result，I found that there are 5%-8% cpu cost on
softirq by use netif_rx_ni called in tun_get_user.
so I changed the function which cause skb transmitted more quickly.
from
tun_get_user ->
netif_rx_ni(skb);
to
tun_get_user ->
rcu_read_lock_bh();
netif_receive_skb(skb);
rcu_read_unlock_bh();
The test result is as below:
CPU: Intel(R) Xeon(R) CPU E5620 @ 2.40GHz
NIC: intel 82599
Host OS/Guest OS:suse11sp3
Qemu-1.6
netperf udp 512(VM tx)
test model: VM->host->host
modified before : 2.00Gbps 461146pps
modified after : 2.16Gbps 498782pps
8% performance gained from this change,
Is there any problem for this patch ?
I think it's okay - IIUC this way we are processing xmit directly
instead of going through softirq.
Was meaning to try this - I'm glad you are looking into this.
Could you please check latency results?
netperf UDP_RR 512
test model: VM->host->host
modified before : 11108
modified after : 11480
3% gained by this patch
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