Re: [RFC] Display the cpu of sched domain in procfs

From: Valentin Schneider
Date: Wed Feb 19 2020 - 05:47:12 EST

On 19/02/2020 10:00, Chen Yu wrote:
>> Now, if you have a userspace that tries to be clever and wants to use this
>> information then yes, this isn't ideal, but then that's a different matter.
> The dmesg might be lost if someone has once used dmesg -c to clear the log,
> and the /var/log/dmesg might not always there. And it is not common to trigger
> sched domain update once boot up in some environment.
> But anyway, this information printed by sched_debug is very fertile for knowing
> the topology.
>> I think exposing the NUMA boundaries is fair game - and they already are
>> via /sys/devices/system/node/node*/.
> It seems that the numa sysfs could not reflect the SNC topology, it just has the
> *leaf* numa node information. Say, node0 and node1 might form one sched_domain.

Right, but if you have leaves + distance table, then userspace can try to
be clever about it without being exposed to scheduler innards.