Documentation: Mention chunk format for irq affinity

PATCH New Sebastian Poehn 1 participant 1 message Jul 22, 2015

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Sebastian Poehn

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2015-07-22 08:09 UTC #0 lore raw

PATCH 1/1 Documentation: Mention chunk format for irq affinity

It may not be obvious for everyone that bitmasks in proc require 32bit chunking

Signed-off-by Sebastian Poehn <[email protected]>

---
 Documentation/IRQ-affinity.txt | 5 +++++
 1 file changed, 5 insertions(+)

Documentation/IRQ-affinity.txt +5 -0

index 01a6751..d873dab 100644
@@ -55,6 +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.
 
+Note that you have to split the bitmask to chunks when using more that 32 cpus:
+[root@moon 44]# echo 80,00000000 > smp_affinity
+[root@moon 44]# cat smp_affinity
+80,00000000
+
 Here is an example of limiting that same irq (44) to cpus 1024 to 1031:
 
 [root@moon 44]# echo 1024-1031 > smp_affinity_list

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