Messages in this thread Patch in this message | | | From | Sudeep Holla <> | Subject | [PATCH v6 17/21] arch_topology: Limit span of cpu_clustergroup_mask() | Date | Mon, 4 Jul 2022 11:16:01 +0100 |
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From: Ionela Voinescu <ionela.voinescu@arm.com>
Currently the cluster identifier is not set on DT based platforms. The reset or default value is -1 for all the CPUs. Once we assign the cluster identifier values correctly, the cluster_sibling mask will be populated and returned by cpu_clustergroup_mask() to contribute in the creation of the CLS scheduling domain level, if SCHED_CLUSTER is enabled.
To avoid topologies that will result in questionable or incorrect scheduling domains, impose restrictions regarding the span of clusters, as presented to scheduling domains building code: cluster_sibling should not span more or the same CPUs as cpu_coregroup_mask().
This is needed in order to obtain a strict separation between the MC and CLS levels, and maintain the same domains for existing platforms in the presence of CONFIG_SCHED_CLUSTER, where the new cluster information is redundant and irrelevant for the scheduler.
While previously the scheduling domain builder code would have removed MC as redundant and kept CLS if SCHED_CLUSTER was enabled and the cpu_coregroup_mask() and cpu_clustergroup_mask() spanned the same CPUs, now CLS will be removed and MC kept.
Cc: Darren Hart <darren@os.amperecomputing.com> Acked-by: Vincent Guittot <vincent.guittot@linaro.org> Tested-by: Ionela Voinescu <ionela.voinescu@arm.com> Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com> Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> --- drivers/base/arch_topology.c | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c index e384afb6cac7..591c1f8e15e2 100644 --- a/drivers/base/arch_topology.c +++ b/drivers/base/arch_topology.c @@ -686,6 +686,14 @@ const struct cpumask *cpu_coregroup_mask(int cpu) const struct cpumask *cpu_clustergroup_mask(int cpu) { + /* + * Forbid cpu_clustergroup_mask() to span more or the same CPUs as + * cpu_coregroup_mask(). + */ + if (cpumask_subset(cpu_coregroup_mask(cpu), + &cpu_topology[cpu].cluster_sibling)) + return get_cpu_mask(cpu); + return &cpu_topology[cpu].cluster_sibling; } -- 2.37.0
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