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