Re: [RESEND PATCH v5 1/2] sched: Add per_cpu cluster domain info and cpus_share_lowest_cache API

From: Vincent Guittot
Date: Wed Jul 20 2022 - 09:56:55 EST

On Wed, 20 Jul 2022 at 10:14, Yicong Yang <yangyicong@xxxxxxxxxxxxx> wrote:
>
> From: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
>
> Add per-cpu cluster domain info and cpus_share_lowest_cache() API.
> This is the preparation for the optimization of select_idle_cpu()
> on platforms with cluster scheduler level.

Don't know why but your patchset ended up in my spam. Peterz
resurected it by replying to patch 2

>
> Tested-by: K Prateek Nayak <kprateek.nayak@xxxxxxx>
> Signed-off-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
> Signed-off-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@xxxxxxx>
> Reviewed-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>

Reviewed-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>


> ---
> include/linux/sched/sd_flags.h | 7 +++++++
> include/linux/sched/topology.h | 8 +++++++-
> kernel/sched/core.c | 12 ++++++++++++
> kernel/sched/sched.h | 2 ++
> kernel/sched/topology.c | 15 +++++++++++++++
> 5 files changed, 43 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/sched/sd_flags.h b/include/linux/sched/sd_flags.h
> index 57bde66d95f7..42ed454e8b18 100644
> --- a/include/linux/sched/sd_flags.h
> +++ b/include/linux/sched/sd_flags.h
> @@ -109,6 +109,13 @@ SD_FLAG(SD_ASYM_CPUCAPACITY_FULL, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS)
> */
> SD_FLAG(SD_SHARE_CPUCAPACITY, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS)
>
> +/*
> + * Domain members share CPU cluster (LLC tags or L2 cache)
> + *
> + * NEEDS_GROUPS: Clusters are shared between groups.
> + */
> +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 816df6cc444e..c0d21667ddf3 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;
> }
> #endif
>
> @@ -179,6 +179,7 @@ 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_lowest_cache(int this_cpu, int that_cpu);
>
> typedef const struct cpumask *(*sched_domain_mask_f)(int cpu);
> typedef int (*sched_domain_flags_f)(void);
> @@ -232,6 +233,11 @@ static inline bool cpus_share_cache(int this_cpu, int that_cpu)
> return true;
> }
>
> +static inline bool cpus_share_lowest_cache(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 a463dbc92fcd..96109ad82694 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3802,6 +3802,18 @@ 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);
> }
>
> +/*
> + * Whether CPUs are share lowest cache, which means LLC on non-cluster
> + * machines and LLC tag or L2 on machines with clusters.
> + */
> +bool cpus_share_lowest_cache(int this_cpu, int that_cpu)
> +{
> + if (this_cpu == that_cpu)
> + return true;
> +
> + return per_cpu(sd_lowest_cache_id, this_cpu) == per_cpu(sd_lowest_cache_id, that_cpu);
> +}
> +
> static inline bool ttwu_queue_cond(int cpu)
> {
> /*
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 73ae32898f25..845cd029d572 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1802,7 +1802,9 @@ 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_lowest_cache_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 8739c2a5a54e..8ab27c0d6d1f 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -664,6 +664,8 @@ 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_lowest_cache_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);
> @@ -689,6 +691,18 @@ 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);
> +
> + /*
> + * This assignment should be placed after the sd_llc_id as
> + * we want this id equals to cluster id on cluster machines
> + * but equals to LLC id on non-Cluster machines.
> + */
> + per_cpu(sd_lowest_cache_id, cpu) = id;
> +
> sd = lowest_flag_domain(cpu, SD_NUMA);
> rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);
>
> @@ -1532,6 +1546,7 @@ static struct cpumask ***sched_domains_numa_masks;
> */
> #define TOPOLOGY_SD_FLAGS \
> (SD_SHARE_CPUCAPACITY | \
> + SD_CLUSTER | \
> SD_SHARE_PKG_RESOURCES | \
> SD_NUMA | \
> SD_ASYM_PACKING)
> --
> 2.24.0
>