Messages in this thread | | | Date | Wed, 22 Dec 2021 15:54:18 +0530 | From | "Gautham R. Shenoy" <> | Subject | Re: [PATCH 1/2] sched: Add per_cpu cluster domain info and cpus_share_cluster API |
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Hello Yicong, Barry,
On Wed, Dec 15, 2021 at 12:11:48PM +0800, Yicong Yang wrote: > From: Barry Song <song.bao.hua@hisilicon.com> > > Add per-cpu cluster domain info and cpus_share_cluster() API. > This is the preparation for the optimization of select_idle_cpu() > on platforms with cluster scheduler level. > > Signed-off-by: Barry Song <song.bao.hua@hisilicon.com> > Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> > --- > include/linux/sched/sd_flags.h | 5 +++++ > include/linux/sched/topology.h | 8 +++++++- > kernel/sched/core.c | 12 ++++++++++++ > kernel/sched/sched.h | 2 ++ > kernel/sched/topology.c | 9 +++++++++ > 5 files changed, 35 insertions(+), 1 deletion(-) > > diff --git a/include/linux/sched/sd_flags.h b/include/linux/sched/sd_flags.h > index 57bde66d95f7..0f732bcfbb2c 100644 > --- a/include/linux/sched/sd_flags.h > +++ b/include/linux/sched/sd_flags.h > @@ -109,6 +109,11 @@ SD_FLAG(SD_ASYM_CPUCAPACITY_FULL, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS) > */ > SD_FLAG(SD_SHARE_CPUCAPACITY, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) > > +/* > + * Set up for cluster domains sharing resources such as llc tags or l2 > + */ > +SD_FLAG(SD_CLUSTER, SDF_NEEDS_GROUPS) > + > /* > * Domain members share CPU package resources (i.e. caches) > * > diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h > index c07bfa2d80f2..78c3a94fae66 100644 > --- a/include/linux/sched/topology.h > +++ b/include/linux/sched/topology.h > @@ -45,7 +45,7 @@ static inline int cpu_smt_flags(void) > #ifdef CONFIG_SCHED_CLUSTER > static inline int cpu_cluster_flags(void) > { > - return SD_SHARE_PKG_RESOURCES; > + return SD_CLUSTER | SD_SHARE_PKG_RESOURCES;
On non-cluster systems, there would be only one group at the at the CLS domain. Since SD_CLUSTER is also tagged with SDF_NEEDS_GROUP, it would need the presence of two groups. Thus, on such non-cluster systems, the CLS domain will continue to be degenerated in favour of the SMT domain.
> } > #endif > > @@ -177,6 +177,7 @@ cpumask_var_t *alloc_sched_domains(unsigned int ndoms); > void free_sched_domains(cpumask_var_t doms[], unsigned int ndoms); > > bool cpus_share_cache(int this_cpu, int that_cpu); > +bool cpus_share_cluster(int this_cpu, int that_cpu); > > typedef const struct cpumask *(*sched_domain_mask_f)(int cpu); > typedef int (*sched_domain_flags_f)(void); > @@ -230,6 +231,11 @@ static inline bool cpus_share_cache(int this_cpu, int that_cpu) > return true; > } > > +static inline bool cpus_share_cluster(int this_cpu, int that_cpu) > +{ > + return true; > +} > + > #endif /* !CONFIG_SMP */ > > #if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL) > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 3c9b0fda64ac..11f9b25c3068 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3732,6 +3732,18 @@ bool cpus_share_cache(int this_cpu, int that_cpu) > return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu); > } > > +/* > + * On non-Cluster machine this function works same with cpus_share_cache() > + * as sd_cluster_id equals to sd_llc_id. > + */
Ok, so on a non-cluster machine, a cluster is trivially defined to be a single core (this is reflected in what the cpu_cluster_mask() shows up on such machines).
However, in cpus_share_cluster(), we are upgrading the definition of a cluster to be group of CPUs that share the LLC. This is inconsistent with the original definition. Is there a way to avoid this inconsistency ?
> +bool cpus_share_cluster(int this_cpu, int that_cpu) > +{ > + if (this_cpu == that_cpu) > + return true; > + > + return per_cpu(sd_cluster_id, this_cpu) == per_cpu(sd_cluster_id, that_cpu); > +} > + > static inline bool ttwu_queue_cond(int cpu, int wake_flags) > { > /* > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index 0e66749486e7..ddd29879ad40 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -1763,7 +1763,9 @@ static inline struct sched_domain *lowest_flag_domain(int cpu, int flag) > DECLARE_PER_CPU(struct sched_domain __rcu *, sd_llc); > DECLARE_PER_CPU(int, sd_llc_size); > DECLARE_PER_CPU(int, sd_llc_id); > +DECLARE_PER_CPU(int, sd_cluster_id); > DECLARE_PER_CPU(struct sched_domain_shared __rcu *, sd_llc_shared); > +DECLARE_PER_CPU(struct sched_domain __rcu *, sd_cluster); > DECLARE_PER_CPU(struct sched_domain __rcu *, sd_numa); > DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing); > DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity); > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index d201a7052a29..5642df384904 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -644,6 +644,8 @@ static void destroy_sched_domains(struct sched_domain *sd) > DEFINE_PER_CPU(struct sched_domain __rcu *, sd_llc); > DEFINE_PER_CPU(int, sd_llc_size); > DEFINE_PER_CPU(int, sd_llc_id); > +DEFINE_PER_CPU(int, sd_cluster_id); > +DEFINE_PER_CPU(struct sched_domain __rcu *, sd_cluster); > DEFINE_PER_CPU(struct sched_domain_shared __rcu *, sd_llc_shared); > DEFINE_PER_CPU(struct sched_domain __rcu *, sd_numa); > DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing); > @@ -669,6 +671,12 @@ static void update_top_cache_domain(int cpu) > per_cpu(sd_llc_id, cpu) = id; > rcu_assign_pointer(per_cpu(sd_llc_shared, cpu), sds); > > + sd = lowest_flag_domain(cpu, SD_CLUSTER); > + if (sd) > + id = cpumask_first(sched_domain_span(sd)); > + rcu_assign_pointer(per_cpu(sd_cluster, cpu), sd); > + per_cpu(sd_cluster_id, cpu) = id; > + > sd = lowest_flag_domain(cpu, SD_NUMA); > rcu_assign_pointer(per_cpu(sd_numa, cpu), sd); > > @@ -1514,6 +1522,7 @@ static unsigned long __read_mostly *sched_numa_onlined_nodes; > */ > #define TOPOLOGY_SD_FLAGS \ > (SD_SHARE_CPUCAPACITY | \ > + SD_CLUSTER | \ > SD_SHARE_PKG_RESOURCES | \ > SD_NUMA | \ > SD_ASYM_PACKING) > -- > 2.33.0 >
-- Thanks and Regards gautham.
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