projects / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 18404756 MK |
1 | ChangeLog: |
| 2 | Started by Ingo Molnar <[email protected]> | |
| 3 | Update by Max Krasnyansky <[email protected]> | |
| 1da177e4 | 4 | |
| 18404756 | 5 | SMP IRQ affinity |
| 1da177e4 LT |
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 | ||
| 18404756 MK |
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 | ||
| 1da177e4 | 17 | Here is an example of restricting IRQ44 (eth1) to CPU0-3 then restricting |
| 18404756 | 18 | it to CPU4-7 (this is an 8-CPU SMP box): |
| 1da177e4 | 19 | |
| 18404756 | 20 | [root@moon 44]# cd /proc/irq/44 |
| 1da177e4 LT |
21 | [root@moon 44]# cat smp_affinity |
| 22 | ffffffff | |
| 18404756 | 23 | |
| 1da177e4 LT |
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 | |
| 18404756 MK |
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 | ||
| 1da177e4 | 41 | [root@moon 44]# echo f0 > smp_affinity |
| 18404756 MK |
42 | [root@moon 44]# cat smp_affinity |
| 43 | 000000f0 | |
| 1da177e4 LT |
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 | |
| 18404756 MK |
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. | |
| 1da177e4 | 56 |