ia64/linux-2.6.18-xen.hg

annotate Documentation/IRQ-affinity.txt @ 854:950b9eb27661

usbback: fix urb interval value for interrupt urbs.

Signed-off-by: Noboru Iwamatsu <n_iwamatsu@jp.fujitsu.com>
author Keir Fraser <keir.fraser@citrix.com>
date Mon Apr 06 13:51:20 2009 +0100 (2009-04-06)
parents 831230e53067
children
rev   line source
ian@0 1
ian@0 2 SMP IRQ affinity, started by Ingo Molnar <mingo@redhat.com>
ian@0 3
ian@0 4
ian@0 5 /proc/irq/IRQ#/smp_affinity specifies which target CPUs are permitted
ian@0 6 for a given IRQ source. It's a bitmask of allowed CPUs. It's not allowed
ian@0 7 to turn off all CPUs, and if an IRQ controller does not support IRQ
ian@0 8 affinity then the value will not change from the default 0xffffffff.
ian@0 9
ian@0 10 Here is an example of restricting IRQ44 (eth1) to CPU0-3 then restricting
ian@0 11 the IRQ to CPU4-7 (this is an 8-CPU SMP box):
ian@0 12
ian@0 13 [root@moon 44]# cat smp_affinity
ian@0 14 ffffffff
ian@0 15 [root@moon 44]# echo 0f > smp_affinity
ian@0 16 [root@moon 44]# cat smp_affinity
ian@0 17 0000000f
ian@0 18 [root@moon 44]# ping -f h
ian@0 19 PING hell (195.4.7.3): 56 data bytes
ian@0 20 ...
ian@0 21 --- hell ping statistics ---
ian@0 22 6029 packets transmitted, 6027 packets received, 0% packet loss
ian@0 23 round-trip min/avg/max = 0.1/0.1/0.4 ms
ian@0 24 [root@moon 44]# cat /proc/interrupts | grep 44:
ian@0 25 44: 0 1785 1785 1783 1783 1
ian@0 26 1 0 IO-APIC-level eth1
ian@0 27 [root@moon 44]# echo f0 > smp_affinity
ian@0 28 [root@moon 44]# ping -f h
ian@0 29 PING hell (195.4.7.3): 56 data bytes
ian@0 30 ..
ian@0 31 --- hell ping statistics ---
ian@0 32 2779 packets transmitted, 2777 packets received, 0% packet loss
ian@0 33 round-trip min/avg/max = 0.1/0.5/585.4 ms
ian@0 34 [root@moon 44]# cat /proc/interrupts | grep 44:
ian@0 35 44: 1068 1785 1785 1784 1784 1069 1070 1069 IO-APIC-level eth1
ian@0 36 [root@moon 44]#
ian@0 37