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

[Vincent Guittot <vincent.guittot@linaro.org>]

On Wed, 20 Jul 2022 at 10:14, Yicong Yang <yangyicong@hisilicon.com> wrote:
>
> From: Barry Song <song.bao.hua@hisilicon.com>
>
> 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@amd.com>
> Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
> Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
> Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com>

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


> ---
>  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
>

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