Re: [RFC PATCH v3 1/2] topology: Represent clusters of CPUs within a die.

From: Masayoshi Mizuma
Date: Tue Feb 09 2021 - 20:23:36 EST

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On Wed, Jan 06, 2021 at 09:30:25PM +1300, Barry Song wrote:
> From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
>
> 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 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@xxxxxxxxxx>
> Signed-off-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
> ---
> -v3:
> * no real change(v2 comments not addressed);
> * rebased againest 5.11-rc2;
>
> Documentation/admin-guide/cputopology.rst | 26 +++++++++++---
> arch/arm64/kernel/topology.c | 2 ++
> drivers/acpi/pptt.c | 60 +++++++++++++++++++++++++++++++
> drivers/base/arch_topology.c | 14 ++++++++
> drivers/base/topology.c | 10 ++++++
> include/linux/acpi.h | 5 +++
> include/linux/arch_topology.h | 5 +++
> include/linux/topology.h | 6 ++++
> 8 files changed, 124 insertions(+), 4 deletions(-)
>
> 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 f6faa69..fe076b3 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..8646a93 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -737,6 +737,66 @@ 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;
> + int retval;
> + int is_thread;
> +
> + status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
> + if (ACPI_FAILURE(status)) {
> + acpi_pptt_warn_missing();
> + return -ENOENT;
> + }

> + cpu_node = acpi_find_processor_node(table, cpu);

The second argument of acpi_find_processor_node() expects ACPI Processor ID,
not the logical cpu number.
How about the following?

acpi_cpu_id = get_acpi_id_for_cpu(cpu);
cpu_node = acpi_find_processor_node(table, acpi_cpu_id);

Thanks,
Masa

> + 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..3079232 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);
> @@ -571,6 +584,7 @@ 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 @@ 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);
>
> @@ -61,6 +64,10 @@ define_siblings_show_func(core_siblings, core_cpumask);
> 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 DEVICE_ATTR_RO(drawer_siblings_list);
> 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 @@ static struct attribute *default_attrs[] = {
> &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 2630c2e..8f603cd 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -1325,6 +1325,7 @@ 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);
> @@ -1337,6 +1338,10 @@ 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 ad03df1..bf2cc3c 100644
> --- a/include/linux/topology.h
> +++ b/include/linux/topology.h
> @@ -185,6 +185,9 @@ 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
> @@ -194,6 +197,9 @@ 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
> --
> 2.7.4
>

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