Initial import of modified Linux 2.6.28 tree

Original upstream URL:
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git | branch linux-2.6.28.y

1 files changed, 56 insertions, 0 deletions

diff --git a/Documentation/IRQ-affinity.txt b/Documentation/IRQ-affinity.txt
new file mode 100644
index 0000000..b4a615b
--- /dev/null
+++ b/Documentation/IRQ-affinity.txt
@@ -0,0 +1,56 @@
+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.
+