APIC seems not working under high network load

[Jia Rao]

Hi all,

I had scalability issues when running memcached-like workloads in a
Intel 8-core system. It turned out that under high network load only
one core handled the interrupts from NIC. In the output of mpstat, one
of the core was overloaded with 100% %soft time. I tried to echo
different core ids to /proc/irq/irq#/smp_affinity, it did not take
effect until I stopped the incoming network traffic. It seems that
APIC is not distributing interrupts to different cores.

The below are the details of the testing system:
OS: Linux 3.1.4 X86_64
CPU: Intel L5450, quad-core
NIC: Intel e1000e

Thanks !
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/