Messages in this thread | | | Subject | Re: [PATCH v8 13/13] arm64: topology: divorce MC scheduling domain from core_siblings | From | Jeremy Linton <> | Date | Wed, 2 May 2018 17:34:14 -0500 |
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Hi,
Thanks for taking a look at this.
On 05/01/2018 09:33 AM, Sudeep Holla wrote: > > > On 26/04/18 00:31, Jeremy Linton wrote: >> Now that we have an accurate view of the physical topology >> we need to represent it correctly to the scheduler. Generally MC >> should equal the LLC in the system, but there are a number of >> special cases that need to be dealt with. >> >> In the case of NUMA in socket, we need to assure that the sched >> domain we build for the MC layer isn't larger than the DIE above it. >> Similarly for LLC's that might exist in cross socket interconnect or >> directory hardware we need to assure that MC is shrunk to the socket >> or NUMA node. >> >> This patch builds a sibling mask for the LLC, and then picks the >> smallest of LLC, socket siblings, or NUMA node siblings, which >> gives us the behavior described above. This is ever so slightly >> different than the similar alternative where we look for a cache >> layer less than or equal to the socket/NUMA siblings. >> >> The logic to pick the MC layer affects all arm64 machines, but >> only changes the behavior for DT/MPIDR systems if the NUMA domain >> is smaller than the core siblings (generally set to the cluster). >> Potentially this fixes a possible bug in DT systems, but really >> it only affects ACPI systems where the core siblings is correctly >> set to the socket siblings. Thus all currently available ACPI >> systems should have MC equal to LLC, including the NUMA in socket >> machines where the LLC is partitioned between the NUMA nodes. >> >> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com> >> --- >> arch/arm64/include/asm/topology.h | 2 ++ >> arch/arm64/kernel/topology.c | 32 +++++++++++++++++++++++++++++++- >> 2 files changed, 33 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h >> index 6b10459e6905..df48212f767b 100644 >> --- a/arch/arm64/include/asm/topology.h >> +++ b/arch/arm64/include/asm/topology.h >> @@ -8,8 +8,10 @@ struct cpu_topology { >> int thread_id; >> int core_id; >> int package_id; >> + int llc_id; >> cpumask_t thread_sibling; >> cpumask_t core_sibling; >> + cpumask_t llc_siblings; >> }; >> >> extern struct cpu_topology cpu_topology[NR_CPUS]; >> diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c >> index bd1aae438a31..20b4341dc527 100644 >> --- a/arch/arm64/kernel/topology.c >> +++ b/arch/arm64/kernel/topology.c >> @@ -13,6 +13,7 @@ >> >> #include <linux/acpi.h> >> #include <linux/arch_topology.h> >> +#include <linux/cacheinfo.h> >> #include <linux/cpu.h> >> #include <linux/cpumask.h> >> #include <linux/init.h> >> @@ -214,7 +215,19 @@ EXPORT_SYMBOL_GPL(cpu_topology); >> >> const struct cpumask *cpu_coregroup_mask(int cpu) >> { >> - return &cpu_topology[cpu].core_sibling; >> + const cpumask_t *core_mask = cpumask_of_node(cpu_to_node(cpu)); >> + >> + /* Find the smaller of NUMA, core or LLC siblings */ >> + if (cpumask_subset(&cpu_topology[cpu].core_sibling, core_mask)) { >> + /* not numa in package, lets use the package siblings */ >> + core_mask = &cpu_topology[cpu].core_sibling; >> + } >> + if (cpu_topology[cpu].llc_id != -1) { >> + if (cpumask_subset(&cpu_topology[cpu].llc_siblings, core_mask)) >> + core_mask = &cpu_topology[cpu].llc_siblings; >> + } >> + >> + return core_mask; >> } >> >> static void update_siblings_masks(unsigned int cpuid) >> @@ -226,6 +239,9 @@ static void update_siblings_masks(unsigned int cpuid) >> for_each_possible_cpu(cpu) { >> cpu_topo = &cpu_topology[cpu]; >> >> + if (cpuid_topo->llc_id == cpu_topo->llc_id) >> + cpumask_set_cpu(cpu, &cpuid_topo->llc_siblings); >> + > > Would this not result in cpuid_topo->llc_siblings = cpu_possible_mask > on DT systems where llc_id is not set/defaults to -1 and still pass the > condition. Does it make sense to add additional -1 check ? (see comment in Morton's thread)
> >> if (cpuid_topo->package_id != cpu_topo->package_id) >> continue; >> >> @@ -291,6 +307,10 @@ static void __init reset_cpu_topology(void) >> cpu_topo->core_id = 0; >> cpu_topo->package_id = -1; >> >> + cpu_topo->llc_id = -1; >> + cpumask_clear(&cpu_topo->llc_siblings); >> + cpumask_set_cpu(cpu, &cpu_topo->llc_siblings); >> + >> cpumask_clear(&cpu_topo->core_sibling); >> cpumask_set_cpu(cpu, &cpu_topo->core_sibling); >> cpumask_clear(&cpu_topo->thread_sibling); >> @@ -311,6 +331,8 @@ static int __init parse_acpi_topology(void) >> is_threaded = read_cpuid_mpidr() & MPIDR_MT_BITMASK; >> >> for_each_possible_cpu(cpu) { >> + int i; >> + >> topology_id = find_acpi_cpu_topology(cpu, 0); >> if (topology_id < 0) >> return topology_id; >> @@ -325,6 +347,14 @@ static int __init parse_acpi_topology(void) >> } >> topology_id = find_acpi_cpu_topology_package(cpu); >> cpu_topology[cpu].package_id = topology_id; >> + >> + i = acpi_find_last_cache_level(cpu); >> + >> + if (i > 0) { >> + topology_id = find_acpi_cpu_cache_topology(cpu, i); >> + if (topology_id > 0) >> + cpu_topology[cpu].llc_id = topology_id; >> + } > > [nit] s/topology_id/cache_id/ or s/topology_id/cache_topology_id/ ?
Sure.
> > Otherwise looks fine to me. You can add with above things fixed. > > Acked-by: Sudeep Holla <sudeep.holla@arm.com> >
Thanks,
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