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bitmap, irq: add smp_affinity_list interface to /proc/irq

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Manually adjusting the smp_affinity for IRQ's becomes unwieldy when the
cpu count is large.

Setting smp affinity to cpus 256 to 263 would be:

	echo 000000ff,00000000,00000000,00000000,00000000,00000000,00000000,00000000 > smp_affinity

instead of:

	echo 256-263 > smp_affinity_list

Think about what it looks like for cpus around say, 4088 to 4095.

We already have many alternate "list" interfaces:

/sys/devices/system/cpu/cpuX/indexY/shared_cpu_list
/sys/devices/system/cpu/cpuX/topology/thread_siblings_list
/sys/devices/system/cpu/cpuX/topology/core_siblings_list
/sys/devices/system/node/nodeX/cpulist
/sys/devices/pci***/***/local_cpulist

Add a companion interface, smp_affinity_list to use cpu lists instead of
cpu maps.  This conforms to other companion interfaces where both a map
and a list interface exists.

This required adding a bitmap_parselist_user() function in a manner
similar to the bitmap_parse_user() function.

[[email protected]: make __bitmap_parselist() static]
Signed-off-by: Mike Travis <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Jack Steiner <[email protected]>
Cc: Lee Schermerhorn <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Mike Travis 2011-05-24 17:13:12 -07:00 • committed by Linus Torvalds
commit 4b060420a5
6 changed files with 188 additions and 23 deletions
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17
Documentation/IRQ-affinity.txt
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@ -4,10 +4,11 @@ ChangeLog:
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/IRQ#/smp_affinity and /proc/irq/IRQ#/smp_affinity_list specify
which target CPUs are permitted for a given IRQ source. It's a bitmask
(smp_affinity) or cpu list (smp_affinity_list) 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 of all cpus.
/proc/irq/default_smp_affinity specifies default affinity mask that applies
to all non-active IRQs. Once IRQ is allocated/activated its affinity bitmask
@ -54,3 +55,11 @@ round-trip min/avg/max = 0.1/0.5/585.4 ms
This time around IRQ44 was delivered only to the last four processors.
i.e counters for the CPU0-3 did not change.
Here is an example of limiting that same irq (44) to cpus 1024 to 1031:
[root@moon 44]# echo 1024-1031 > smp_affinity
[root@moon 44]# cat smp_affinity
1024-1031
Note that to do this with a bitmask would require 32 bitmasks of zero
to follow the pertinent one.