| SMP IRQ affinity, started by Ingo Molnar <mingo@redhat.com> | |
| /proc/irq/IRQ#/smp_affinity specifies which target CPUs are permitted | |
| for a given IRQ source. It's a bitmask of allowed CPUs. It's not allowed | |
| to turn off all CPUs, and if an IRQ controller does not support IRQ | |
| affinity then the value will not change from the default 0xffffffff. | |
| Here is an example of restricting IRQ44 (eth1) to CPU0-3 then restricting | |
| the IRQ to CPU4-7 (this is an 8-CPU SMP box): | |
| [root@moon 44]# cat smp_affinity | |
| ffffffff | |
| [root@moon 44]# echo 0f > smp_affinity | |
| [root@moon 44]# cat smp_affinity | |
| 0000000f | |
| [root@moon 44]# ping -f h | |
| PING hell (195.4.7.3): 56 data bytes | |
| ... | |
| --- hell ping statistics --- | |
| 6029 packets transmitted, 6027 packets received, 0% packet loss | |
| round-trip min/avg/max = 0.1/0.1/0.4 ms | |
| [root@moon 44]# cat /proc/interrupts | grep 44: | |
| 44: 0 1785 1785 1783 1783 1 | |
| 1 0 IO-APIC-level eth1 | |
| [root@moon 44]# echo f0 > smp_affinity | |
| [root@moon 44]# ping -f h | |
| PING hell (195.4.7.3): 56 data bytes | |
| .. | |
| --- hell ping statistics --- | |
| 2779 packets transmitted, 2777 packets received, 0% packet loss | |
| round-trip min/avg/max = 0.1/0.5/585.4 ms | |
| [root@moon 44]# cat /proc/interrupts | grep 44: | |
| 44: 1068 1785 1785 1784 1784 1069 1070 1069 IO-APIC-level eth1 | |
| [root@moon 44]# | |