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Source at commit 6c17a31f1fc515425221067cb3ece599c09dbc5d created 12 years 8 months ago. By Werner Almesberger, atusb, atben: moved from spi/ to ieee802154/; renamed atusb to spi_atusb | |
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1 | ChangeLog: |
2 | Started by Ingo Molnar <mingo@redhat.com> |
3 | Update by Max Krasnyansky <maxk@qualcomm.com> |
4 | |
5 | SMP IRQ affinity |
6 | |
7 | /proc/irq/IRQ#/smp_affinity specifies which target CPUs are permitted |
8 | for a given IRQ source. It's a bitmask of allowed CPUs. It's not allowed |
9 | to turn off all CPUs, and if an IRQ controller does not support IRQ |
10 | affinity then the value will not change from the default 0xffffffff. |
11 | |
12 | /proc/irq/default_smp_affinity specifies default affinity mask that applies |
13 | to all non-active IRQs. Once IRQ is allocated/activated its affinity bitmask |
14 | will be set to the default mask. It can then be changed as described above. |
15 | Default mask is 0xffffffff. |
16 | |
17 | Here is an example of restricting IRQ44 (eth1) to CPU0-3 then restricting |
18 | it to CPU4-7 (this is an 8-CPU SMP box): |
19 | |
20 | [root@moon 44]# cd /proc/irq/44 |
21 | [root@moon 44]# cat smp_affinity |
22 | ffffffff |
23 | |
24 | [root@moon 44]# echo 0f > smp_affinity |
25 | [root@moon 44]# cat smp_affinity |
26 | 0000000f |
27 | [root@moon 44]# ping -f h |
28 | PING hell (195.4.7.3): 56 data bytes |
29 | ... |
30 | --- hell ping statistics --- |
31 | 6029 packets transmitted, 6027 packets received, 0% packet loss |
32 | round-trip min/avg/max = 0.1/0.1/0.4 ms |
33 | [root@moon 44]# cat /proc/interrupts | grep 'CPU\|44:' |
34 | CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 CPU6 CPU7 |
35 | 44: 1068 1785 1785 1783 0 0 0 0 IO-APIC-level eth1 |
36 | |
37 | As can be seen from the line above IRQ44 was delivered only to the first four |
38 | processors (0-3). |
39 | Now lets restrict that IRQ to CPU(4-7). |
40 | |
41 | [root@moon 44]# echo f0 > smp_affinity |
42 | [root@moon 44]# cat smp_affinity |
43 | 000000f0 |
44 | [root@moon 44]# ping -f h |
45 | PING hell (195.4.7.3): 56 data bytes |
46 | .. |
47 | --- hell ping statistics --- |
48 | 2779 packets transmitted, 2777 packets received, 0% packet loss |
49 | round-trip min/avg/max = 0.1/0.5/585.4 ms |
50 | [root@moon 44]# cat /proc/interrupts | 'CPU\|44:' |
51 | CPU0 CPU1 CPU2 CPU3 CPU4 CPU5 CPU6 CPU7 |
52 | 44: 1068 1785 1785 1783 1784 1069 1070 1069 IO-APIC-level eth1 |
53 | |
54 | This time around IRQ44 was delivered only to the last four processors. |
55 | i.e counters for the CPU0-3 did not change. |
56 | |
57 |
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