Re: [PATCH] sched/topology: Enable topology_span_sane check only for debug builds

[Valentin Schneider]

On 22/10/24 10:57, Saurabh Sengar wrote:
> On a x86 system under test with 1780 CPUs, topology_span_sane() takes
> around 8 seconds cumulatively for all the iterations. It is an expensive
> operation which does the sanity of non-NUMA topology masks.
>
> CPU topology is not something which changes very frequently hence make
> this check optional for the systems where the topology is trusted and
> need faster bootup.
>
> Restrict this to SCHED_DEBUG builds so that this penalty can be avoided
> for the systems who wants to avoid it.
>
> Fixes: ccf74128d66c ("sched/topology: Assert non-NUMA topology masks don't (partially) overlap")
> Signed-off-by: Saurabh Sengar <ssengar@xxxxxxxxxxxxxxxxxxx>

Please see:
http://lore.kernel.org/r/20241010155111.230674-1-steve.wahl@xxxxxxx

Also note that most distros ship with CONFIG_SCHED_DEBUG=y, so while I'm
not 100% against it this would at the very least need to be gated behind
e.g. the sched_verbose cmdline argument to be useful.

But before that I'd like the "just run it once" option to be explored
first.