Re: Spreading NIC interrupts across multiple CPUs
On 3/26/2014 2:44 PM, Stan Hoeppner wrote:
Please read this for educational background, especially the Note at the
bottom of the page.
https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Performance_Tuning_Guide/s-cpu-irq.html
Then ask an intelligent question about IRQ balancing and steering, WRT
the two specific and different hardware systems, and Debian kernel
versions, being used on each.
I'd seen other things similar to that, however, it doesn't seem to get
me any closer to the solution.
The output from one of the Dell (not balanced) systems:
root@conf-2:~# uname -a
Linux conf-2 3.2.0-4-amd64 #1 SMP Debian 3.2.54-2 x86_64 GNU/Linux
root@conf-2:~# grep eth /proc/interrupts
79: 704642666 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 PCI-MSI-edge eth0
root@conf-2:~# cat /proc/irq/79/smp_affinity
0000ffff
root@conf-2:~# cat /proc/irq/79/smp_affinity_list
0-15
The output from the HP (balanced) system:
root@deb-test:~# grep eth /proc/interrupts
68: 4251 4190 4212 4264 4226 4257
4251 4214 PCI-MSI-edge eth0
root@deb-test:~# cat /proc/irq/68/smp_affinity
ff
root@deb-test:~# cat /proc/irq/68/smp_affinity_list
0-7
As you can see, both systems are running identical kernels, and both
have affinity set to spread across all CPUs. However, the Dell is using
CPU0 exclusively for the ethernet device interrupts, while the HP
spreads them pretty evenly.
Thanks,
-Aaron
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