IRQ-affinity.txt 1.3 KB

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  1. SMP IRQ affinity, started by Ingo Molnar <mingo@redhat.com>
  2. /proc/irq/IRQ#/smp_affinity specifies which target CPUs are permitted
  3. for a given IRQ source. It's a bitmask of allowed CPUs. It's not allowed
  4. to turn off all CPUs, and if an IRQ controller does not support IRQ
  5. affinity then the value will not change from the default 0xffffffff.
  6. Here is an example of restricting IRQ44 (eth1) to CPU0-3 then restricting
  7. the IRQ to CPU4-7 (this is an 8-CPU SMP box):
  8. [root@moon 44]# cat smp_affinity
  9. ffffffff
  10. [root@moon 44]# echo 0f > smp_affinity
  11. [root@moon 44]# cat smp_affinity
  12. 0000000f
  13. [root@moon 44]# ping -f h
  14. PING hell (195.4.7.3): 56 data bytes
  15. ...
  16. --- hell ping statistics ---
  17. 6029 packets transmitted, 6027 packets received, 0% packet loss
  18. round-trip min/avg/max = 0.1/0.1/0.4 ms
  19. [root@moon 44]# cat /proc/interrupts | grep 44:
  20. 44: 0 1785 1785 1783 1783 1
  21. 1 0 IO-APIC-level eth1
  22. [root@moon 44]# echo f0 > smp_affinity
  23. [root@moon 44]# ping -f h
  24. PING hell (195.4.7.3): 56 data bytes
  25. ..
  26. --- hell ping statistics ---
  27. 2779 packets transmitted, 2777 packets received, 0% packet loss
  28. round-trip min/avg/max = 0.1/0.5/585.4 ms
  29. [root@moon 44]# cat /proc/interrupts | grep 44:
  30. 44: 1068 1785 1785 1784 1784 1069 1070 1069 IO-APIC-level eth1
  31. [root@moon 44]#