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

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Message-ID: <422b5d06-ec0e-f064-32fe-15df5b2957dd@linux.intel.com>
Date:   Tue, 20 Apr 2021 11:31:38 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
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Subject: 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:

>>
>> On 3/18/21 9:16 PM, Barry Song wrote:
>>> From: Tim Chen <tim.c.chen@...ux.intel.com>
>>>
>>> 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 <tim.c.chen@...ux.intel.com>
>>> Signed-off-by: Barry Song <song.bao.hua@...ilicon.com>
>>
>>
>> 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;