Re: [RFC PATCH v4 1/3] topology: Represent clusters of CPUs within a die.

From: Jonathan Cameron
Date: Mon Mar 15 2021 - 06:54:05 EST

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On Mon, 15 Mar 2021 03:11:06 +0000
"Song Bao Hua (Barry Song)" <song.bao.hua@xxxxxxxxxxxxx> wrote:

> > -----Original Message-----
> > From: Song Bao Hua (Barry Song)
> > Sent: Tuesday, March 2, 2021 12:00 PM
> > To: tim.c.chen@xxxxxxxxxxxxxxx; catalin.marinas@xxxxxxx; will@xxxxxxxxxx;
> > rjw@xxxxxxxxxxxxx; vincent.guittot@xxxxxxxxxx; bp@xxxxxxxxx;
> > tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; lenb@xxxxxxxxxx; peterz@xxxxxxxxxxxxx;
> > dietmar.eggemann@xxxxxxx; rostedt@xxxxxxxxxxx; bsegall@xxxxxxxxxx;
> > mgorman@xxxxxxx
> > Cc: msys.mizuma@xxxxxxxxx; valentin.schneider@xxxxxxx;
> > gregkh@xxxxxxxxxxxxxxxxxxx; Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>;
> > juri.lelli@xxxxxxxxxx; mark.rutland@xxxxxxx; sudeep.holla@xxxxxxx;
> > aubrey.li@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > linux-kernel@xxxxxxxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx; x86@xxxxxxxxxx;
> > xuwei (O) <xuwei5@xxxxxxxxxx>; Zengtao (B) <prime.zeng@xxxxxxxxxxxxx>;
> > guodong.xu@xxxxxxxxxx; yangyicong <yangyicong@xxxxxxxxxx>; Liguozhu (Kenneth)
> > <liguozhu@xxxxxxxxxxxxx>; linuxarm@xxxxxxxxxxxxx; hpa@xxxxxxxxx; Jonathan
> > Cameron <jonathan.cameron@xxxxxxxxxx>; Song Bao Hua (Barry Song)
> > <song.bao.hua@xxxxxxxxxxxxx>
> > Subject: [RFC PATCH v4 1/3] topology: Represent clusters of CPUs within a die.
> >
> > 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 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@xxxxxxxxxx>
> > Signed-off-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
> > ---
> > -v4:
> > * used acpi_cpu_id for acpi_find_processor_node(addressing Masa's comment)
> >
> > Documentation/admin-guide/cputopology.rst | 26 +++++++++++--
> > arch/arm64/kernel/topology.c | 2 +
> > drivers/acpi/pptt.c | 63 +++++++++++++++++++++++++++++++
> > 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, 127 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..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..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);
> > + }
> > +
>
> I am seeing a machine without cluster is getting cluster,
> so I guess we need the below:

Makes sense and is inline with the docs above.

Thanks,

Jonathan

>
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 3079232ed8ed..ccd4b3b5cc6f 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -528,7 +528,8 @@ 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) {
> + if (cpuid_topo->cluster_id == cpu_topo->cluster_id &&
> + cpu_topo->cluster_id != -1) {
> cpumask_set_cpu(cpu, &cpuid_topo->cluster_sibling);
> cpumask_set_cpu(cpuid, &cpu_topo->cluster_sibling);
> }
> @@ -568,6 +569,7 @@ void __init reset_cpu_topology(void)
> struct cpu_topology *cpu_topo = &cpu_topology[cpu];
>
> cpu_topo->thread_id = -1;
> + cpu_topo->cluster_id = -1;
> cpu_topo->core_id = -1;
> cpu_topo->package_id = -1;
> cpu_topo->llc_id = -1;
>
> Hi Jonathan, thoughts?
>
> Thanks
> Barry
>

Next message: Christophe Leroy: "Re: Build regressions/improvements in v5.12-rc3"
Previous message: Ian Abbott: "Re: [PATCH] staging: comedi: cb_pcidas: replace slash in name"
In reply to: Song Bao Hua (Barry Song): "RE: [RFC PATCH v4 1/3] topology: Represent clusters of CPUs within a die."
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