[RFC,v6,1/4] topology: Represent clusters of CPUs within a die

Message ID 20210420001844.9116-2-song.bao.hua@hisilicon.com
State New
Headers show
Series
  • scheduler: expose the topology of clusters and add cluster scheduler
Related show

Commit Message

Song Bao Hua (Barry Song) April 20, 2021, 12:18 a.m.
From: Jonathan Cameron <Jonathan.Cameron@huawei.com>


Both ACPI and DT provide the ability to describe additional layers of
topology between that of individual cores and higher level constructs
such as the level at which the last level cache is shared.
In ACPI this can be represented in PPTT as a Processor Hierarchy
Node Structure [1] that is the parent of the CPU cores and in turn
has a parent Processor Hierarchy Nodes Structure representing
a higher level of topology.

For example Kunpeng 920 has 6 or 8 clusters in each NUMA node, and each
cluster has 4 cpus. All clusters share L3 cache data, but each cluster
has local L3 tag. On the other hand, each clusters will share some
internal system bus.

+-----------------------------------+                          +---------+
|  +------+    +------+            +---------------------------+         |
|  | CPU0 |    | cpu1 |             |    +-----------+         |         |
|  +------+    +------+             |    |           |         |         |
|                                   +----+    L3     |         |         |
|  +------+    +------+   cluster   |    |    tag    |         |         |
|  | CPU2 |    | CPU3 |             |    |           |         |         |
|  +------+    +------+             |    +-----------+         |         |
|                                   |                          |         |
+-----------------------------------+                          |         |
+-----------------------------------+                          |         |
|  +------+    +------+             +--------------------------+         |
|  |      |    |      |             |    +-----------+         |         |
|  +------+    +------+             |    |           |         |         |
|                                   |    |    L3     |         |         |
|  +------+    +------+             +----+    tag    |         |         |
|  |      |    |      |             |    |           |         |         |
|  +------+    +------+             |    +-----------+         |         |
|                                   |                          |         |
+-----------------------------------+                          |   L3    |
                                                               |   data  |
+-----------------------------------+                          |         |
|  +------+    +------+             |    +-----------+         |         |
|  |      |    |      |             |    |           |         |         |
|  +------+    +------+             +----+    L3     |         |         |
|                                   |    |    tag    |         |         |
|  +------+    +------+             |    |           |         |         |
|  |      |    |      |            ++    +-----------+         |         |
|  +------+    +------+            |---------------------------+         |
+-----------------------------------|                          |         |
+-----------------------------------|                          |         |
|  +------+    +------+            +---------------------------+         |
|  |      |    |      |             |    +-----------+         |         |
|  +------+    +------+             |    |           |         |         |
|                                   +----+    L3     |         |         |
|  +------+    +------+             |    |    tag    |         |         |
|  |      |    |      |             |    |           |         |         |
|  +------+    +------+             |    +-----------+         |         |
|                                   |                          |         |
+-----------------------------------+                          |         |
+-----------------------------------+                          |         |
|  +------+    +------+             +--------------------------+         |
|  |      |    |      |             |   +-----------+          |         |
|  +------+    +------+             |   |           |          |         |
|                                   |   |    L3     |          |         |
|  +------+    +------+             +---+    tag    |          |         |
|  |      |    |      |             |   |           |          |         |
|  +------+    +------+             |   +-----------+          |         |
|                                   |                          |         |
+-----------------------------------+                          |         |
+-----------------------------------+                         ++         |
|  +------+    +------+             +--------------------------+         |
|  |      |    |      |             |  +-----------+           |         |
|  +------+    +------+             |  |           |           |         |
|                                   |  |    L3     |           |         |
|  +------+    +------+             +--+    tag    |           |         |
|  |      |    |      |             |  |           |           |         |
|  +------+    +------+             |  +-----------+           |         |
|                                   |                          +---------+
+-----------------------------------+

That means the cost to transfer ownership of a cacheline between CPUs
within a cluster is lower than between CPUs in different clusters on
the same die. Hence, it can make sense to tell the scheduler to use
the cache affinity of the cluster to make better decision on thread
migration.

This patch simply exposes this information to userspace libraries
like hwloc by providing cluster_cpus and related sysfs attributes.
PoC of HWLOC support at [2].

Note this patch only handle the ACPI case.

Special consideration is needed for SMT processors, where it is
necessary to move 2 levels up the hierarchy from the leaf nodes
(thus skipping the processor core level).

Currently the ID provided is the offset of the Processor
Hierarchy Nodes Structure within PPTT.  Whilst this is unique
it is not terribly elegant so alternative suggestions welcome.

Note that arm64 / ACPI does not provide any means of identifying
a die level in the topology but that may be unrelate to the cluster
level.

[1] ACPI Specification 6.3 - section 5.2.29.1 processor hierarchy node
    structure (Type 0)
[2] https://github.com/hisilicon/hwloc/tree/linux-cluster

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>

---
 -v6:
 * the topology ABI documents required by Greg is not completed yet.
   will have a separate patch for that.

 Documentation/admin-guide/cputopology.rst | 26 +++++++++++--
 arch/arm64/kernel/topology.c              |  2 +
 drivers/acpi/pptt.c                       | 63 +++++++++++++++++++++++++++++++
 drivers/base/arch_topology.c              | 15 ++++++++
 drivers/base/topology.c                   | 10 +++++
 include/linux/acpi.h                      |  5 +++
 include/linux/arch_topology.h             |  5 +++
 include/linux/topology.h                  |  6 +++
 8 files changed, 128 insertions(+), 4 deletions(-)

-- 
1.8.3.1

Comments

Andrew Jones April 28, 2021, 9:48 a.m. | #1
On 20/04/2021 12:18, Barry Song wrote:
...
> Currently the ID provided is the offset of the Processor

> Hierarchy Nodes Structure within PPTT.  Whilst this is unique

> it is not terribly elegant so alternative suggestions welcome.

> 


The ACPI table offsets are consistent with how other topology IDs are
generated. I once tried to make them a little more human friendly with
[1], but it was nacked.

[1] https://lore.kernel.org/lkml/20180629132934.GA16282@e107155-lin/t/

Thanks,
drew
Song Bao Hua (Barry Song) April 30, 2021, 3:46 a.m. | #2
> -----Original Message-----

> From: Andrew Jones [mailto:drjones@redhat.com]

> Sent: Wednesday, April 28, 2021 9:48 PM

> To: Song Bao Hua (Barry Song) <song.bao.hua@hisilicon.com>

> Cc: aubrey.li@linux.intel.com; bp@alien8.de; bsegall@google.com;

> catalin.marinas@arm.com; dietmar.eggemann@arm.com;

> gregkh@linuxfoundation.org; guodong.xu@linaro.org; hpa@zytor.com; Jonathan

> Cameron <jonathan.cameron@huawei.com>; juri.lelli@redhat.com;

> lenb@kernel.org; Liguozhu (Kenneth) <liguozhu@hisilicon.com>;

> linux-acpi@vger.kernel.org; linux-arm-kernel@lists.infradead.org;

> linux-kernel@vger.kernel.org; linuxarm@openeuler.org; mark.rutland@arm.com;

> mgorman@suse.de; mingo@redhat.com; msys.mizuma@gmail.com;

> peterz@infradead.org; Zengtao (B) <prime.zeng@hisilicon.com>;

> rjw@rjwysocki.net; rostedt@goodmis.org; sudeep.holla@arm.com;

> tglx@linutronix.de; tim.c.chen@linux.intel.com; valentin.schneider@arm.com;

> vincent.guittot@linaro.org; will@kernel.org; x86@kernel.org; xuwei (O)

> <xuwei5@huawei.com>; yangyicong <yangyicong@huawei.com>

> Subject: Re: [RFC PATCH v6 1/4] topology: Represent clusters of CPUs within

> a die

> 

> On 20/04/2021 12:18, Barry Song wrote:

> ...

> > Currently the ID provided is the offset of the Processor

> > Hierarchy Nodes Structure within PPTT.  Whilst this is unique

> > it is not terribly elegant so alternative suggestions welcome.

> >

> 

> The ACPI table offsets are consistent with how other topology IDs are

> generated. I once tried to make them a little more human friendly with

> [1], but it was nacked.

> 

> [1] https://lore.kernel.org/lkml/20180629132934.GA16282@e107155-lin/t/

> 


Ideally, we are going to check if cluster node has a valid UID,
if yes, read this ID; otherwise, fall back to use offset.

Will move to that way in next version.

> Thanks,

> drew


Thanks
Barry

Patch

diff --git a/Documentation/admin-guide/cputopology.rst b/Documentation/admin-guide/cputopology.rst
index b90dafc..f9d3745 100644
--- a/Documentation/admin-guide/cputopology.rst
+++ b/Documentation/admin-guide/cputopology.rst
@@ -24,6 +24,12 @@  core_id:
 	identifier (rather than the kernel's).  The actual value is
 	architecture and platform dependent.
 
+cluster_id:
+
+	the Cluster ID of cpuX.  Typically it is the hardware platform's
+	identifier (rather than the kernel's).  The actual value is
+	architecture and platform dependent.
+
 book_id:
 
 	the book ID of cpuX. Typically it is the hardware platform's
@@ -56,6 +62,14 @@  package_cpus_list:
 	human-readable list of CPUs sharing the same physical_package_id.
 	(deprecated name: "core_siblings_list")
 
+cluster_cpus:
+
+	internal kernel map of CPUs within the same cluster.
+
+cluster_cpus_list:
+
+	human-readable list of CPUs within the same cluster.
+
 die_cpus:
 
 	internal kernel map of CPUs within the same die.
@@ -96,11 +110,13 @@  these macros in include/asm-XXX/topology.h::
 
 	#define topology_physical_package_id(cpu)
 	#define topology_die_id(cpu)
+	#define topology_cluster_id(cpu)
 	#define topology_core_id(cpu)
 	#define topology_book_id(cpu)
 	#define topology_drawer_id(cpu)
 	#define topology_sibling_cpumask(cpu)
 	#define topology_core_cpumask(cpu)
+	#define topology_cluster_cpumask(cpu)
 	#define topology_die_cpumask(cpu)
 	#define topology_book_cpumask(cpu)
 	#define topology_drawer_cpumask(cpu)
@@ -116,10 +132,12 @@  not defined by include/asm-XXX/topology.h:
 
 1) topology_physical_package_id: -1
 2) topology_die_id: -1
-3) topology_core_id: 0
-4) topology_sibling_cpumask: just the given CPU
-5) topology_core_cpumask: just the given CPU
-6) topology_die_cpumask: just the given CPU
+3) topology_cluster_id: -1
+4) topology_core_id: 0
+5) topology_sibling_cpumask: just the given CPU
+6) topology_core_cpumask: just the given CPU
+7) topology_cluster_cpumask: just the given CPU
+8) topology_die_cpumask: just the given CPU
 
 For architectures that don't support books (CONFIG_SCHED_BOOK) there are no
 default definitions for topology_book_id() and topology_book_cpumask().
diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index e08a412..d72eb8d 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -103,6 +103,8 @@  int __init parse_acpi_topology(void)
 			cpu_topology[cpu].thread_id  = -1;
 			cpu_topology[cpu].core_id    = topology_id;
 		}
+		topology_id = find_acpi_cpu_topology_cluster(cpu);
+		cpu_topology[cpu].cluster_id = topology_id;
 		topology_id = find_acpi_cpu_topology_package(cpu);
 		cpu_topology[cpu].package_id = topology_id;
 
diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index 4ae9335..11f8b02 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -737,6 +737,69 @@  int find_acpi_cpu_topology_package(unsigned int cpu)
 }
 
 /**
+ * find_acpi_cpu_topology_cluster() - Determine a unique CPU cluster value
+ * @cpu: Kernel logical CPU number
+ *
+ * Determine a topology unique cluster ID for the given CPU/thread.
+ * This ID can then be used to group peers, which will have matching ids.
+ *
+ * The cluster, if present is the level of topology above CPUs. In a
+ * multi-thread CPU, it will be the level above the CPU, not the thread.
+ * It may not exist in single CPU systems. In simple multi-CPU systems,
+ * it may be equal to the package topology level.
+ *
+ * Return: -ENOENT if the PPTT doesn't exist, the CPU cannot be found
+ * or there is no toplogy level above the CPU..
+ * Otherwise returns a value which represents the package for this CPU.
+ */
+
+int find_acpi_cpu_topology_cluster(unsigned int cpu)
+{
+	struct acpi_table_header *table;
+	acpi_status status;
+	struct acpi_pptt_processor *cpu_node, *cluster_node;
+	u32 acpi_cpu_id;
+	int retval;
+	int is_thread;
+
+	status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
+	if (ACPI_FAILURE(status)) {
+		acpi_pptt_warn_missing();
+		return -ENOENT;
+	}
+
+	acpi_cpu_id = get_acpi_id_for_cpu(cpu);
+	cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
+	if (cpu_node == NULL || !cpu_node->parent) {
+		retval = -ENOENT;
+		goto put_table;
+	}
+
+	is_thread = cpu_node->flags & ACPI_PPTT_ACPI_PROCESSOR_IS_THREAD;
+	cluster_node = fetch_pptt_node(table, cpu_node->parent);
+	if (cluster_node == NULL) {
+		retval = -ENOENT;
+		goto put_table;
+	}
+	if (is_thread) {
+		if (!cluster_node->parent) {
+			retval = -ENOENT;
+			goto put_table;
+		}
+		cluster_node = fetch_pptt_node(table, cluster_node->parent);
+		if (cluster_node == NULL) {
+			retval = -ENOENT;
+			goto put_table;
+		}
+	}
+	retval = ACPI_PTR_DIFF(cluster_node, table);
+put_table:
+	acpi_put_table(table);
+
+	return retval;
+}
+
+/**
  * find_acpi_cpu_topology_hetero_id() - Get a core architecture tag
  * @cpu: Kernel logical CPU number
  *
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index de8587c..ca3b8c1 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -506,6 +506,11 @@  const struct cpumask *cpu_coregroup_mask(int cpu)
 	return core_mask;
 }
 
+const struct cpumask *cpu_clustergroup_mask(int cpu)
+{
+	return &cpu_topology[cpu].cluster_sibling;
+}
+
 void update_siblings_masks(unsigned int cpuid)
 {
 	struct cpu_topology *cpu_topo, *cpuid_topo = &cpu_topology[cpuid];
@@ -523,6 +528,11 @@  void update_siblings_masks(unsigned int cpuid)
 		if (cpuid_topo->package_id != cpu_topo->package_id)
 			continue;
 
+		if (cpuid_topo->cluster_id == cpu_topo->cluster_id) {
+			cpumask_set_cpu(cpu, &cpuid_topo->cluster_sibling);
+			cpumask_set_cpu(cpuid, &cpu_topo->cluster_sibling);
+		}
+
 		cpumask_set_cpu(cpuid, &cpu_topo->core_sibling);
 		cpumask_set_cpu(cpu, &cpuid_topo->core_sibling);
 
@@ -541,6 +551,9 @@  static void clear_cpu_topology(int cpu)
 	cpumask_clear(&cpu_topo->llc_sibling);
 	cpumask_set_cpu(cpu, &cpu_topo->llc_sibling);
 
+	cpumask_clear(&cpu_topo->cluster_sibling);
+	cpumask_set_cpu(cpu, &cpu_topo->cluster_sibling);
+
 	cpumask_clear(&cpu_topo->core_sibling);
 	cpumask_set_cpu(cpu, &cpu_topo->core_sibling);
 	cpumask_clear(&cpu_topo->thread_sibling);
@@ -556,6 +569,7 @@  void __init reset_cpu_topology(void)
 
 		cpu_topo->thread_id = -1;
 		cpu_topo->core_id = -1;
+		cpu_topo->cluster_id = -1;
 		cpu_topo->package_id = -1;
 		cpu_topo->llc_id = -1;
 
@@ -571,6 +585,7 @@  void remove_cpu_topology(unsigned int cpu)
 		cpumask_clear_cpu(cpu, topology_core_cpumask(sibling));
 	for_each_cpu(sibling, topology_sibling_cpumask(cpu))
 		cpumask_clear_cpu(cpu, topology_sibling_cpumask(sibling));
+
 	for_each_cpu(sibling, topology_llc_cpumask(cpu))
 		cpumask_clear_cpu(cpu, topology_llc_cpumask(sibling));
 
diff --git a/drivers/base/topology.c b/drivers/base/topology.c
index 4d254fc..7157ac0 100644
--- a/drivers/base/topology.c
+++ b/drivers/base/topology.c
@@ -46,6 +46,9 @@ 
 define_id_show_func(die_id);
 static DEVICE_ATTR_RO(die_id);
 
+define_id_show_func(cluster_id);
+static DEVICE_ATTR_RO(cluster_id);
+
 define_id_show_func(core_id);
 static DEVICE_ATTR_RO(core_id);
 
@@ -61,6 +64,10 @@ 
 static DEVICE_ATTR_RO(core_siblings);
 static DEVICE_ATTR_RO(core_siblings_list);
 
+define_siblings_show_func(cluster_cpus, cluster_cpumask);
+static DEVICE_ATTR_RO(cluster_cpus);
+static DEVICE_ATTR_RO(cluster_cpus_list);
+
 define_siblings_show_func(die_cpus, die_cpumask);
 static DEVICE_ATTR_RO(die_cpus);
 static DEVICE_ATTR_RO(die_cpus_list);
@@ -88,6 +95,7 @@ 
 static struct attribute *default_attrs[] = {
 	&dev_attr_physical_package_id.attr,
 	&dev_attr_die_id.attr,
+	&dev_attr_cluster_id.attr,
 	&dev_attr_core_id.attr,
 	&dev_attr_thread_siblings.attr,
 	&dev_attr_thread_siblings_list.attr,
@@ -95,6 +103,8 @@ 
 	&dev_attr_core_cpus_list.attr,
 	&dev_attr_core_siblings.attr,
 	&dev_attr_core_siblings_list.attr,
+	&dev_attr_cluster_cpus.attr,
+	&dev_attr_cluster_cpus_list.attr,
 	&dev_attr_die_cpus.attr,
 	&dev_attr_die_cpus_list.attr,
 	&dev_attr_package_cpus.attr,
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 9f43241..138b779 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1307,6 +1307,7 @@  static inline int lpit_read_residency_count_address(u64 *address)
 #ifdef CONFIG_ACPI_PPTT
 int acpi_pptt_cpu_is_thread(unsigned int cpu);
 int find_acpi_cpu_topology(unsigned int cpu, int level);
+int find_acpi_cpu_topology_cluster(unsigned int cpu);
 int find_acpi_cpu_topology_package(unsigned int cpu);
 int find_acpi_cpu_topology_hetero_id(unsigned int cpu);
 int find_acpi_cpu_cache_topology(unsigned int cpu, int level);
@@ -1319,6 +1320,10 @@  static inline int find_acpi_cpu_topology(unsigned int cpu, int level)
 {
 	return -EINVAL;
 }
+static inline int find_acpi_cpu_topology_cluster(unsigned int cpu)
+{
+	return -EINVAL;
+}
 static inline int find_acpi_cpu_topology_package(unsigned int cpu)
 {
 	return -EINVAL;
diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index 0f6cd6b..987c7ea 100644
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -49,10 +49,12 @@  void topology_set_thermal_pressure(const struct cpumask *cpus,
 struct cpu_topology {
 	int thread_id;
 	int core_id;
+	int cluster_id;
 	int package_id;
 	int llc_id;
 	cpumask_t thread_sibling;
 	cpumask_t core_sibling;
+	cpumask_t cluster_sibling;
 	cpumask_t llc_sibling;
 };
 
@@ -60,13 +62,16 @@  struct cpu_topology {
 extern struct cpu_topology cpu_topology[NR_CPUS];
 
 #define topology_physical_package_id(cpu)	(cpu_topology[cpu].package_id)
+#define topology_cluster_id(cpu)	(cpu_topology[cpu].cluster_id)
 #define topology_core_id(cpu)		(cpu_topology[cpu].core_id)
 #define topology_core_cpumask(cpu)	(&cpu_topology[cpu].core_sibling)
 #define topology_sibling_cpumask(cpu)	(&cpu_topology[cpu].thread_sibling)
+#define topology_cluster_cpumask(cpu)	(&cpu_topology[cpu].cluster_sibling)
 #define topology_llc_cpumask(cpu)	(&cpu_topology[cpu].llc_sibling)
 void init_cpu_topology(void);
 void store_cpu_topology(unsigned int cpuid);
 const struct cpumask *cpu_coregroup_mask(int cpu);
+const struct cpumask *cpu_clustergroup_mask(int cpu);
 void update_siblings_masks(unsigned int cpu);
 void remove_cpu_topology(unsigned int cpuid);
 void reset_cpu_topology(void);
diff --git a/include/linux/topology.h b/include/linux/topology.h
index 7634cd7..80d27d7 100644
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -186,6 +186,9 @@  static inline int cpu_to_mem(int cpu)
 #ifndef topology_die_id
 #define topology_die_id(cpu)			((void)(cpu), -1)
 #endif
+#ifndef topology_cluster_id
+#define topology_cluster_id(cpu)		((void)(cpu), -1)
+#endif
 #ifndef topology_core_id
 #define topology_core_id(cpu)			((void)(cpu), 0)
 #endif
@@ -195,6 +198,9 @@  static inline int cpu_to_mem(int cpu)
 #ifndef topology_core_cpumask
 #define topology_core_cpumask(cpu)		cpumask_of(cpu)
 #endif
+#ifndef topology_cluster_cpumask
+#define topology_cluster_cpumask(cpu)		cpumask_of(cpu)
+#endif
 #ifndef topology_die_cpumask
 #define topology_die_cpumask(cpu)		cpumask_of(cpu)
 #endif