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Revision 0ea457839d050370e0f7c75c81f9abd573e1f420 authored by Linus Torvalds on 10 February 2010, 15:15:21 UTC, committed by Linus Torvalds on 10 February 2010, 15:15:21 UTC 
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6
 
* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-2.6: (29 commits)
  drivers/net: Correct NULL test
  MAINTAINERS: networking drivers - Add git net-next tree
  net/sched: Fix module name in Kconfig
  cxgb3: fix GRO checksum check
  dst: call cond_resched() in dst_gc_task()
  netfilter: nf_conntrack: fix hash resizing with namespaces
  netfilter: xtables: compat out of scope fix
  netfilter: nf_conntrack: restrict runtime expect hashsize modifications
  netfilter: nf_conntrack: per netns nf_conntrack_cachep
  netfilter: nf_conntrack: fix memory corruption with multiple namespaces
  Bluetooth: Keep a copy of each HID device's report descriptor
  pktgen: Fix freezing problem
  igb: make certain to reassign legacy interrupt vectors after reset
  irda: add missing BKL in irnet_ppp ioctl
  irda: unbalanced lock_kernel in irnet_ppp
  ixgbe: Fix return of invalid txq
  ixgbe: Fix ixgbe_tx_map error path
  netxen: protect resource cleanup by rtnl lock
  netxen: fix tx timeout recovery for NX2031 chip
  Bluetooth: Enter active mode before establishing a SCO link.
  ...
2 parent s ac73fdd + 44bfce5
Raw File
IRQ-affinity.txt 
ChangeLog:
	Started by Ingo Molnar <mingo@redhat.com>
	Update by Max Krasnyansky <maxk@qualcomm.com>

SMP IRQ affinity

/proc/irq/IRQ#/smp_affinity specifies which target CPUs are permitted
for a given IRQ source. It's a bitmask of allowed CPUs. It's not allowed
to turn off all CPUs, and if an IRQ controller does not support IRQ
affinity then the value will not change from the default 0xffffffff.

/proc/irq/default_smp_affinity specifies default affinity mask that applies
to all non-active IRQs. Once IRQ is allocated/activated its affinity bitmask
will be set to the default mask. It can then be changed as described above.
Default mask is 0xffffffff.

Here is an example of restricting IRQ44 (eth1) to CPU0-3 then restricting
it to CPU4-7 (this is an 8-CPU SMP box):

[root@moon 44]# cd /proc/irq/44
[root@moon 44]# cat smp_affinity
ffffffff

[root@moon 44]# echo 0f > smp_affinity
[root@moon 44]# cat smp_affinity
0000000f
[root@moon 44]# ping -f h
PING hell (195.4.7.3): 56 data bytes
...
--- hell ping statistics ---
6029 packets transmitted, 6027 packets received, 0% packet loss
round-trip min/avg/max = 0.1/0.1/0.4 ms
[root@moon 44]# cat /proc/interrupts | grep 'CPU\|44:'
           CPU0       CPU1       CPU2       CPU3      CPU4       CPU5        CPU6       CPU7
 44:       1068       1785       1785       1783         0          0           0         0    IO-APIC-level  eth1

As can be seen from the line above IRQ44 was delivered only to the first four
processors (0-3).
Now lets restrict that IRQ to CPU(4-7).

[root@moon 44]# echo f0 > smp_affinity
[root@moon 44]# cat smp_affinity
000000f0
[root@moon 44]# ping -f h
PING hell (195.4.7.3): 56 data bytes
..
--- hell ping statistics ---
2779 packets transmitted, 2777 packets received, 0% packet loss
round-trip min/avg/max = 0.1/0.5/585.4 ms
[root@moon 44]# cat /proc/interrupts |  'CPU\|44:'
           CPU0       CPU1       CPU2       CPU3      CPU4       CPU5        CPU6       CPU7
 44:       1068       1785       1785       1783      1784       1069        1070       1069   IO-APIC-level  eth1

This time around IRQ44 was delivered only to the last four processors.
i.e counters for the CPU0-3 did not change.
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