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topology: Represent clusters of CPUs within a die

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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 spreading tasks among clusters will bring more bandwidth
while packing tasks within one cluster will lead to smaller cache
synchronization latency. So both kernel and userspace will have
a chance to leverage this topology to deploy tasks accordingly to
achieve either smaller cache latency within one cluster or an even
distribution of load among clusters for higher throughput.

This patch exposes cluster topology to both kernel and userspace.
Libraried like hwloc will know cluster by 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).

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: Tian Tao <tiantao6@hisilicon.com>
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210924085104.44806-2-21cnbao@gmail.com
This commit is contained in:
Jonathan Cameron 2021-09-24 20:51:02 +12:00 committed by Peter Zijlstra
parent 37b47298ab
commit c5e22feffd
9 changed files with 133 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
Documentation/ABI/stable/sysfs-devices-system-cpu
View File

@ -42,6 +42,12 @@ Description: the CPU core ID of cpuX. Typically it is the hardware platform's
architecture and platform dependent.
Values: integer
What: /sys/devices/system/cpu/cpuX/topology/cluster_id
Description: 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.
Values: integer
What: /sys/devices/system/cpu/cpuX/topology/book_id
Description: the book ID of cpuX. Typically it is the hardware platform's
identifier (rather than the kernel's). The actual value is
@ -85,6 +91,15 @@ Description: human-readable list of CPUs within the same die.
The format is like 0-3, 8-11, 14,17.
Values: decimal list.
What: /sys/devices/system/cpu/cpuX/topology/cluster_cpus
Description: internal kernel map of CPUs within the same cluster.
Values: hexadecimal bitmask.
What: /sys/devices/system/cpu/cpuX/topology/cluster_cpus_list
Description: human-readable list of CPUs within the same cluster.
The format is like 0-3, 8-11, 14,17.
Values: decimal list.
What: /sys/devices/system/cpu/cpuX/topology/book_siblings
Description: internal kernel map of cpuX's hardware threads within the same
book_id. it's only used on s390.

12
Documentation/admin-guide/cputopology.rst
View File

@ -19,11 +19,13 @@ 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)
@ -39,10 +41,12 @@ 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().

2
arch/arm64/kernel/topology.c
View File

@ -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;

67
drivers/acpi/pptt.c
View File

@ -746,6 +746,73 @@ int find_acpi_cpu_topology_package(unsigned int cpu)
ACPI_PPTT_PHYSICAL_PACKAGE);
}
/**
* 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;
}
}
if (cluster_node->flags & ACPI_PPTT_ACPI_PROCESSOR_ID_VALID)
retval = cluster_node->acpi_processor_id;
else
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

15
drivers/base/arch_topology.c
View File

@ -600,6 +600,11 @@ 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];
@ -617,6 +622,12 @@ 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 &&
cpuid_topo->cluster_id != -1) {
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);
@ -635,6 +646,9 @@ 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);
@ -650,6 +664,7 @@ 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;

10
drivers/base/topology.c
View File

@ -48,6 +48,9 @@ static DEVICE_ATTR_RO(physical_package_id);
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);
@ -63,6 +66,10 @@ define_siblings_read_func(core_siblings, core_cpumask);
static BIN_ATTR_RO(core_siblings, 0);
static BIN_ATTR_RO(core_siblings_list, 0);
define_siblings_read_func(cluster_cpus, cluster_cpumask);
static BIN_ATTR_RO(cluster_cpus, 0);
static BIN_ATTR_RO(cluster_cpus_list, 0);
define_siblings_read_func(die_cpus, die_cpumask);
static BIN_ATTR_RO(die_cpus, 0);
static BIN_ATTR_RO(die_cpus_list, 0);
@ -94,6 +101,8 @@ static struct bin_attribute *bin_attrs[] = {
&bin_attr_thread_siblings_list,
&bin_attr_core_siblings,
&bin_attr_core_siblings_list,
&bin_attr_cluster_cpus,
&bin_attr_cluster_cpus_list,
&bin_attr_die_cpus,
&bin_attr_die_cpus_list,
&bin_attr_package_cpus,
@ -112,6 +121,7 @@ static struct bin_attribute *bin_attrs[] = {
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,
#ifdef CONFIG_SCHED_BOOK
&dev_attr_book_id.attr,

5
include/linux/acpi.h
View File

@ -1353,6 +1353,7 @@ 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);
@ -1365,6 +1366,10 @@ 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;

5
include/linux/arch_topology.h
View File

@ -62,10 +62,12 @@ 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;
};
@ -73,13 +75,16 @@ 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);

6
include/linux/topology.h
View File

@ -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