From: Jens Axboe Date: Fri, 5 Dec 2008 11:57:11 +0000 (+0100) Subject: Add comment on cpumask not working with a CPU count > 32 X-Git-Tag: fio-1.24~36 X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=b0ea08ce4ed567d3dff372f0866d5c3fbf1f8c39 Add comment on cpumask not working with a CPU count > 32 Signed-off-by: Jens Axboe --- diff --git a/HOWTO b/HOWTO index 4298f324..5a55c1a2 100644 --- a/HOWTO +++ b/HOWTO @@ -583,7 +583,10 @@ cpumask=int Set the CPU affinity of this job. The parameter given is a 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