Subject: [PATCH] Documentation: Mention chunk format for irq affinity

From: Sebastian Poehn <[email-masked]>
Date: Wed, 22 Jul 2015 10:09:36 +0200

It may not be obvious for everyone that bitmasks in proc require
32bit chunking
    
Signed-off-by: Sebastian Poehn <[email-masked]>
---
 Documentation/IRQ-affinity.txt | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/IRQ-affinity.txt b/Documentation/IRQ-affinity.txt
index 01a6751..d873dab 100644
--- a/Documentation/IRQ-affinity.txt
+++ b/Documentation/IRQ-affinity.txt
@@ -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
-- 
2.4.3