Re: [RFC PATCH v5 4/4] scheduler: Add cluster scheduler level for x86

On 3/23/21 4:21 PM, Song Bao Hua (Barry Song) wrote:

quoted

On 3/18/21 9:16 PM, Barry Song wrote:

quoted

From: Tim Chen <redacted>

There are x86 CPU architectures (e.g. Jacobsville) where L2 cahce
is shared among a cluster of cores instead of being exclusive
to one single core.

To prevent oversubscription of L2 cache, load should be
balanced between such L2 clusters, especially for tasks with
no shared data.

Also with cluster scheduling policy where tasks are woken up
in the same L2 cluster, we will benefit from keeping tasks
related to each other and likely sharing data in the same L2
cluster.

Add CPU masks of CPUs sharing the L2 cache so we can build such
L2 cluster scheduler domain.

Signed-off-by: Tim Chen <redacted>
Signed-off-by: Barry Song <redacted>

Barry,

Can you also add this chunk to the patch.
Thanks.

Sure, Tim, Thanks. I'll put that into patch 4/4 in v6.

Barry,

This chunk will also need to be added to return cluster id for x86.
Please add it in your next rev.

Thanks.

Tim

---

diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index 800fa48c9fcd..2548d824f103 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h

@@ -109,6 +109,7 @@ extern const struct cpumask *cpu_clustergroup_mask(int cpu);
 #define topology_physical_package_id(cpu)	(cpu_data(cpu).phys_proc_id)
 #define topology_logical_die_id(cpu)		(cpu_data(cpu).logical_die_id)
 #define topology_die_id(cpu)			(cpu_data(cpu).cpu_die_id)
+#define topology_cluster_id(cpu)		(per_cpu(cpu_l2c_id, cpu))
 #define topology_core_id(cpu)			(cpu_data(cpu).cpu_core_id)
 
 extern unsigned int __max_die_per_package;

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