Messages in this thread Patch in this message | | | From | Vincent Guittot <> | Date | Wed, 22 Dec 2021 14:33:37 +0100 | Subject | Re: [PATCH 1/2] sched: Add per_cpu cluster domain info and cpus_share_cluster API |
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On Wed, 22 Dec 2021 at 14:14, Vincent Guittot <vincent.guittot@linaro.org> wrote: > > On Wed, 22 Dec 2021 at 12:06, Barry Song <21cnbao@gmail.com> wrote: > > > > On Wed, Dec 22, 2021 at 11:24 PM Gautham R. Shenoy > > <gautham.shenoy@amd.com> wrote: > > > > > > 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 ? > > > > Hi gautham, > > Yep but I wrote this trick to keep the change in patch2/2 compatible > > with non-cluster machine: > > > > @@ -6384,7 +6422,7 @@ static int select_idle_sibling(struct > > task_struct *p, int prev, int target) > > /* > > * If the previous CPU is cache affine and idle, don't be stupid: > > */ > > - if (prev != target && cpus_share_cache(prev, target) && > > + if (prev != target && cpus_share_cluster(prev, target) && > > (available_idle_cpu(prev) || sched_idle_cpu(prev)) && > > asym_fits_capacity(task_util, prev)) > > return prev; > > @@ -6408,7 +6446,7 @@ static int select_idle_sibling(struct > > task_struct *p, int prev, int target) > > p->recent_used_cpu = prev; > > if (recent_used_cpu != prev && > > recent_used_cpu != target && > > - cpus_share_cache(recent_used_cpu, target) && > > + cpus_share_cluster(recent_used_cpu, target) && > > (available_idle_cpu(recent_used_cpu) || sched_idle_cpu(recent_used_cpu)) && > > cpumask_test_cpu(p->recent_used_cpu, p->cpus_ptr) && > > asym_fits_capacity(task_util, recent_used_cpu)) { > > @@ -6449,7 +6487,7 @@ static int select_idle_sibling(struct > > task_struct *p, int prev, int target) > > } > > } > > > > I didn't find a better way to implement this with minimum overhead and > > code modification. > > > > > > > > > > > > > > > +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; > > > > + > > This deserves a large comment to highlight that the new code above is > not self contained and relies on the fact that it is done just after > looking for LLC and sd and that id and sd must not be changed in > between inorder to ensures that per_cpu(sd_cluster_id, cpu) equals > per_cpu(sd_llc_id, cpu) if there is no domain with SD_CLUSTER. > > and per_cpu(sd_cluster_id, cpu) might not be cluster but llc
Maybe you should not name this sd_cluster_id at all but per_cpu(sd_share_id, cpu) = id;
Then you have a function named
+bool cpus_share_resources(int this_cpu, int that_cpu) +{ + if (this_cpu == that_cpu) + return true; + + return per_cpu(sd_share_id, this_cpu) == per_cpu(sd_share_id, that_cpu); +} + which returns true when cpu shares resources which can be LLC or cluster
> > > > > 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. > > > > Thanks > > Barry
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