Add comment on cpumask not working with a CPU count > 32
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/HOWTO b/HOWTO
index 4298f32..5a55c1a 100644
--- a/HOWTO
+++ b/HOWTO
@@ -583,7 +583,10 @@
the allowed CPUs to be 1 and 5, you would pass the decimal
value of (1 << 1 | 1 << 5), or 34. See man
sched_setaffinity(2). This may not work on all supported
- operating systems or kernel versions.
+ operating systems or kernel versions. This option doesn't
+ work well for a higher CPU count than what you can store in
+ an integer mask, so it can only control cpus 1-32. For
+ boxes with larger CPU counts, use cpus_allowed.
cpus_allowed=str Controls the same options as cpumask, but it allows a text
setting of the permitted CPUs instead. So to use CPUs 1 and