Messages in this thread | | | Date | Fri, 23 Mar 2018 00:20:30 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2] x86,sched: allow topologies where NUMA nodes share an LLC |
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On Thu, Mar 22, 2018 at 01:49:22PM -0700, Alison Schofield wrote: > + /* > + * Some Intel CPUs enumerate an LLC that is shared by > + * multiple NUMA nodes. The LLC on these systems is > + * shared for off-package data access but private to the > + * NUMA node (half of the package) for on-package access. > + * > + * CPUID can only enumerate the cache as being shared *or* > + * unshared, but not this particular configuration. The > + * CPU in this case enumerates the cache to be shared > + * across the entire package (spanning both NUMA nodes). > + */ > + if (!topology_same_node(c, o) && > + (c->x86_vendor == X86_VENDOR_INTEL && > + c->x86_model == INTEL_FAM6_SKYLAKE_X)) { > + /* Use NUMA instead of coregroups for scheduling: */ > + x86_has_numa_in_package = true; > + > + /* > + * Return value doesn't actually matter because we > + * are throwing away coregroups for scheduling anyway. > + * Return false to bypass topology broken bug messages > + * and fixups in sched_domain(). > + */ > + return false;
IIRC that return value _does_ matter because the resulting mask still ends up user visible in sysfs.
IIRC I went over with this dhansen a week or so ago, but I cannot now recall what we settled on as being the right return value and for what reason.
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