Quick question on the Linux networking stack. When in SMP mode, will the Linux networking stack run on multiple cores?

For example:
We have Program A running on core 0, Program B running on core 1, and 1 ethernet port (eth0).
Say A and B each send a packet which will be transmitted on eth0. When the packets are being processed by the kernel network stack, they would potentially be processed in seperate cores (probably 0 and 1 based on the cores A and B are running on) correct?

Or is there some point at which processing of packets is scheduled on a particular core?

When the packet is passed to the network card driver, there must be a send lock so that access to the tx ring is synchronized....

Thanks,
Zack

Good question!

Here's an excellent article that discusses the issues, and some solutions for the 2.6.x kernel:

http://www.alexonlinux.com/smp-affin...dling-in-linux

Here's the official kernel documentation on "IRQ affinity":

http://www.mjmwired.net/kernel/Docum...Q-affinity.txt

And a good article discussing what it means:

http://software.intel.com/en-us/arti...ssor-affinity/

'Hope that helps .. PSM

Hey PSM,

Thanks for your reply. I think what you are referring to is only relevant for received packets, correct?

I was talking more about packets being sent out by applications, which would be syscall-driven rather than interrupt-driven...

Thanks,
Zack