Re: [PATCH v8 13/13] arm64: topology: divorce MC scheduling domain from core_siblings

[Morten Rasmussen <morten.rasmussen@arm.com>]

On Wed, Apr 25, 2018 at 06:31:21PM -0500, Jeremy Linton wrote:
> Now that we have an accurate view of the physical topology
> we need to represent it correctly to the scheduler. Generally MC
> should equal the LLC in the system, but there are a number of
> special cases that need to be dealt with.
> 
> In the case of NUMA in socket, we need to assure that the sched
> domain we build for the MC layer isn't larger than the DIE above it.
> Similarly for LLC's that might exist in cross socket interconnect or
> directory hardware we need to assure that MC is shrunk to the socket
> or NUMA node.
> 
> This patch builds a sibling mask for the LLC, and then picks the
> smallest of LLC, socket siblings, or NUMA node siblings, which
> gives us the behavior described above. This is ever so slightly
> different than the similar alternative where we look for a cache
> layer less than or equal to the socket/NUMA siblings.
> 
> The logic to pick the MC layer affects all arm64 machines, but
> only changes the behavior for DT/MPIDR systems if the NUMA domain
> is smaller than the core siblings (generally set to the cluster).
> Potentially this fixes a possible bug in DT systems, but really
> it only affects ACPI systems where the core siblings is correctly
> set to the socket siblings. Thus all currently available ACPI
> systems should have MC equal to LLC, including the NUMA in socket
> machines where the LLC is partitioned between the NUMA nodes.
> 
> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>

This patch looks good to me.

Acked-by: Morten Rasmussen <morten.rasmussen@arm.com>