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authorMax Krasnyansky <maxk@qualcomm.com>2008-05-29 11:02:52 -0700
committerThomas Gleixner <tglx@linutronix.de>2008-06-05 15:18:30 +0200
commit18404756765c713a0be4eb1082920c04822ce588 (patch)
treeed426f8fe90bff1ffd854074a2e4b370dd6821f8 /Documentation/filesystems
parentc3b25b32e8bef526cca748e1ba023c6bdd705a99 (diff)
genirq: Expose default irq affinity mask (take 3)
Current IRQ affinity interface does not provide a way to set affinity for the IRQs that will be allocated/activated in the future. This patch creates /proc/irq/default_smp_affinity that lets users set default affinity mask for the newly allocated IRQs. Changing the default does not affect affinity masks for the currently active IRQs, they have to be changed explicitly. Updated based on Paul J's comments and added some more documentation. Signed-off-by: Max Krasnyansky <maxk@qualcomm.com> Cc: pj@sgi.com Cc: a.p.zijlstra@chello.nl Cc: tglx@linutronix.de Cc: rdunlap@xenotime.net Cc: mingo@elte.hu Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/proc.txt29
1 files changed, 18 insertions, 11 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index dbc3c6a3650..7f268f327d7 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -380,28 +380,35 @@ i386 and x86_64 platforms support the new IRQ vector displays.
Of some interest is the introduction of the /proc/irq directory to 2.4.
It could be used to set IRQ to CPU affinity, this means that you can "hook" an
IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
-irq subdir is one subdir for each IRQ, and one file; prof_cpu_mask
+irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
+prof_cpu_mask.
For example
> ls /proc/irq/
0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
- 1 11 13 15 17 19 3 5 7 9
+ 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
> ls /proc/irq/0/
smp_affinity
-The contents of the prof_cpu_mask file and each smp_affinity file for each IRQ
-is the same by default:
+smp_affinity is a bitmask, in which you can specify which CPUs can handle the
+IRQ, you can set it by doing:
- > cat /proc/irq/0/smp_affinity
- ffffffff
+ > echo 1 > /proc/irq/10/smp_affinity
+
+This means that only the first CPU will handle the IRQ, but you can also echo
+5 which means that only the first and fourth CPU can handle the IRQ.
-It's a bitmask, in which you can specify which CPUs can handle the IRQ, you can
-set it by doing:
+The contents of each smp_affinity file is the same by default:
+
+ > cat /proc/irq/0/smp_affinity
+ ffffffff
- > echo 1 > /proc/irq/prof_cpu_mask
+The default_smp_affinity mask applies to all non-active IRQs, which are the
+IRQs which have not yet been allocated/activated, and hence which lack a
+/proc/irq/[0-9]* directory.
-This means that only the first CPU will handle the IRQ, but you can also echo 5
-which means that only the first and fourth CPU can handle the IRQ.
+prof_cpu_mask specifies which CPUs are to be profiled by the system wide
+profiler. Default value is ffffffff (all cpus).
The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
between all the CPUs which are allowed to handle it. As usual the kernel has