Hi Jeremy,
On 2017/9/15 2:49, Jeremy Linton wrote:
> Propagate the topology information from the PPTT tree to the
> cpu_topology array. We can get the thread id, core_id and
> cluster_id by assuming certain levels of the PPTT tree correspond
> to those concepts. The package_id is flagged in the tree and can be
> found by passing an arbitrary large level to setup_acpi_cpu_topology()
> which terminates its search when it finds an ACPI node flagged
> as the physical package. If the tree doesn't contain enough
> levels to represent all of thread/core/cod/package then the package
> id will be used for the missing levels.
>
> Since arm64 machines can have 3 distinct topology levels, and the
> scheduler only handles sockets/threads well today, we compromise
> by collapsing into one of three diffrent configurations. These are
> thread/socket, thread/cluster or cluster/socket depending on whether
> the machine has threading and multisocket, threading in a single
> socket, or doesn't have threading.
>
> This code is loosely based on a combination of code from:
> Xiongfeng Wang <wangxiongfeng2@xxxxxxxxxx>
> John Garry <john.garry@xxxxxxxxxx>
> Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>
>
> Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
> ---
> arch/arm64/kernel/topology.c | 68 +++++++++++++++++++++++++++++++++++++++++++-
> include/linux/topology.h | 2 ++
> 2 files changed, 69 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
> index 9147e5b6326d..8ee5cc5ba9bd 100644
> --- a/arch/arm64/kernel/topology.c
> +++ b/arch/arm64/kernel/topology.c
> @@ -11,6 +11,7 @@
> * for more details.
> */
>
> +#include <linux/acpi.h>
> #include <linux/arch_topology.h>
> #include <linux/cpu.h>
> #include <linux/cpumask.h>
> @@ -22,6 +23,7 @@
> #include <linux/sched.h>
> #include <linux/sched/topology.h>
> #include <linux/slab.h>
> +#include <linux/smp.h>
> #include <linux/string.h>
>
> #include <asm/cpu.h>
> @@ -304,6 +306,68 @@ static void __init reset_cpu_topology(void)
> }
> }
>
> +#ifdef CONFIG_ACPI
> +/*
> + * Propagate the topology information of the processor_topology_node tree to the
> + * cpu_topology array.
> + */
> +static int __init parse_acpi_topology(void)
> +{
> + u64 is_threaded;
> + int is_multisocket;
> + int cpu;
> + int topology_id;
> + /* set a large depth, to hit ACPI_PPTT_PHYSICAL_PACKAGE if one exists */
> + const int max_topo = 0xFF;
> +
> + is_threaded = read_cpuid_mpidr() & MPIDR_MT_BITMASK;
> + is_multisocket = acpi_multisocket_count();
> + if (is_multisocket < 0)
> + return is_multisocket;
> +
> + for_each_possible_cpu(cpu) {
> + topology_id = setup_acpi_cpu_topology(cpu, 0);
> + if (topology_id < 0)
> + return topology_id;
> +
> + if ((is_threaded) && (is_multisocket > 1)) {
> + /* MT per core, and multiple sockets */
> + cpu_topology[cpu].thread_id = topology_id;
> + topology_id = setup_acpi_cpu_topology(cpu, 1);
> + cpu_topology[cpu].core_id = topology_id;
> + topology_id = setup_acpi_cpu_topology(cpu, 2);
> + cpu_topology[cpu].cluster_id = topology_id;
> + topology_id = setup_acpi_cpu_topology(cpu, max_topo);
> + cpu_topology[cpu].package_id = topology_id;
> + } else if (is_threaded) {
> + /* mutltiple threads, but only a single socket */
> + cpu_topology[cpu].thread_id = topology_id;
> + topology_id = setup_acpi_cpu_topology(cpu, 1);
> + cpu_topology[cpu].core_id = topology_id;
> + topology_id = setup_acpi_cpu_topology(cpu, 2);
> + cpu_topology[cpu].cluster_id = topology_id;
> + cpu_topology[cpu].package_id = topology_id;
> + } else {
> + /* no threads, clusters behave like threads */
> + cpu_topology[cpu].thread_id = topology_id;
> + topology_id = setup_acpi_cpu_topology(cpu, 1);
> + cpu_topology[cpu].core_id = topology_id;
> + cpu_topology[cpu].cluster_id = topology_id;
> + topology_id = setup_acpi_cpu_topology(cpu, max_topo);
> + cpu_topology[cpu].package_id = topology_id;
I can not understand why should we consider cores in a cluster as threads. The scheduler will
be effected a lot by this. And the 'lstopo' may display wrong information.
Thanks,
Xiongfeng Wang
> + }
> + }
> + return 0;
> +}
> +
> +#else
> +static int __init parse_acpi_topology(void)
> +{
> + /*ACPI kernels should be built with PPTT support*/
> + return -EINVAL;
> +}
> +#endif
> +
> void __init init_cpu_topology(void)
> {
> reset_cpu_topology();
> @@ -312,6 +376,8 @@ void __init init_cpu_topology(void)
> * Discard anything that was parsed if we hit an error so we
> * don't use partial information.
> */
> - if (of_have_populated_dt() && parse_dt_topology())
> + if ((!acpi_disabled) && parse_acpi_topology())
> + reset_cpu_topology();
> + else if (of_have_populated_dt() && parse_dt_topology())
> reset_cpu_topology();
> }
> diff --git a/include/linux/topology.h b/include/linux/topology.h
> index 4660749a7303..08bf736be7c1 100644
> --- a/include/linux/topology.h
> +++ b/include/linux/topology.h
> @@ -43,6 +43,8 @@
> if (nr_cpus_node(node))
>
> int arch_update_cpu_topology(void);
> +int setup_acpi_cpu_topology(unsigned int cpu, int level);
> +int acpi_multisocket_count(void);
>
> /* Conform to ACPI 2.0 SLIT distance definitions */
> #define LOCAL_DISTANCE 10
>
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