vhost_net module TX path is expensive?

vhost_net module TX path is expensive?

[Tushar Swain]

Hi,

I am running a VM in Linux-kvm (kernel 3.6.11-4 ) that uses vhost_net
driver for sending/receiving traffic in backend. VM has two ports and
the stack running in the VM functions like a simple router that
receives packet from one virtual port and simply routes it to other
virtual port. In the backend, vhost_net driver does the actual packet
handling for VM.

In my routing test, the vhost_net TX path seems to be twice expensive
than RX packet.

For a 1500 byte packet, "sendmsg" socket call in "handle_tx" routine in
"drivers/vhost/net.c"  takes almost twice the time than "recvmsg"
socket call in "handle_rx" routine

sendmsg takes ~12000 cycles
recvmsg takes ~6000 cycles

Is there any thing wrong?
Is there any way to minimize the time taken in sendmsg call?

Thanks
TS

vhost_net module TX path is expensive?

[Tushar Swain]

Hi,

I am running a VM in Linux-kvm (kernel 3.6.11-4 ) that uses vhost_net
driver for sending/receiving traffic in backend. VM has two ports and
the stack running in the VM functions like a simple router that
receives packet from one virtual port and simply routes it to other
virtual port. In the backend, vhost_net driver does the actual packet
handling for VM.

In my routing test, the vhost_net TX path seems to be twice expensive
than RX packet.

The "sendmsg" socket call in "handle_tx" routine in
"drivers/vhost/net.c"  takes almost twice the time than "recvmsg"
socket call in "handle_rx" routine

sendmsg takes ~12000 cycles
recvmsg takes ~6000 cycles

Is there any thing wrong?
Is there any way to minimize the time taken in sendmsg call?

Thanks
TS