| Message ID | 20220630065527.38544-3-yangyicong@hisilicon.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | sched/fair: Scan cluster before scanning LLC in wake-up path | expand |
Hi, a friendly ping.. On 2022/6/30 14:55, Yicong Yang wrote: > From: Barry Song <song.bao.hua@hisilicon.com> > > For platforms having clusters like Kunpeng920, CPUs within the same cluster > have lower latency when synchronizing and accessing shared resources like > cache. Thus, this patch tries to find an idle cpu within the cluster of the > target CPU before scanning the whole LLC to gain lower latency. > > Note neither Kunpeng920 nor x86 Jacobsville supports SMT, so this patch > doesn't consider SMT for this moment. > > Testing has been done on Kunpeng920 by pinning tasks to one numa and two > numa. On Kunpeng920, Each numa has 8 clusters and each cluster has 4 CPUs. > > With this patch, We noticed enhancement on tbench within one numa or cross > two numa. > > On numa 0: > tip/core patched > Hmean 1 345.89 ( 0.00%) 393.96 * 13.90%* > Hmean 2 697.77 ( 0.00%) 786.04 * 12.65%* > Hmean 4 1392.51 ( 0.00%) 1570.26 * 12.76%* > Hmean 8 2800.61 ( 0.00%) 3083.98 * 10.12%* > Hmean 16 5514.27 ( 0.00%) 6116.00 * 10.91%* > Hmean 32 10869.81 ( 0.00%) 10782.98 * -0.80%* > Hmean 64 8315.22 ( 0.00%) 8519.84 * 2.46%* > Hmean 128 6324.47 ( 0.00%) 7159.35 * 13.20%* > > On numa 0-1: > tip/core patched > Hmean 1 348.68 ( 0.00%) 387.91 * 11.25%* > Hmean 2 693.57 ( 0.00%) 774.91 * 11.73%* > Hmean 4 1369.26 ( 0.00%) 1475.48 * 7.76%* > Hmean 8 2772.99 ( 0.00%) 2984.61 * 7.63%* > Hmean 16 4825.83 ( 0.00%) 5873.13 * 21.70%* > Hmean 32 10250.32 ( 0.00%) 11688.06 * 14.03%* > Hmean 64 16309.51 ( 0.00%) 19889.48 * 21.95%* > Hmean 128 13022.32 ( 0.00%) 16005.64 * 22.91%* > Hmean 256 11335.79 ( 0.00%) 13821.74 * 21.93%* > > Tested-by: Yicong Yang <yangyicong@hisilicon.com> > Signed-off-by: Barry Song <song.bao.hua@hisilicon.com> > Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> > Reviewed-by: Tim Chen <tim.c.chen@linux.intel.com> > --- > kernel/sched/fair.c | 44 +++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 41 insertions(+), 3 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index f80ae86bb404..dff5dec0d792 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6323,6 +6323,40 @@ static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd > > #endif /* CONFIG_SCHED_SMT */ > > +#ifdef CONFIG_SCHED_CLUSTER > +/* > + * Scan the cluster domain for idle CPUs and clear cluster cpumask after scanning > + */ > +static inline int scan_cluster(struct task_struct *p, struct cpumask *cpus, > + int target, int *nr) > +{ > + struct sched_domain *sd = rcu_dereference(per_cpu(sd_cluster, target)); > + int cpu, idle_cpu; > + > + /* TODO: Support SMT system with cluster topology */ > + if (!sched_smt_active() && sd) { > + for_each_cpu_and(cpu, cpus, sched_domain_span(sd)) { > + if (!--*nr) > + return -1; > + > + idle_cpu = __select_idle_cpu(cpu, p); > + if ((unsigned int)idle_cpu < nr_cpumask_bits) > + return idle_cpu; > + } > + > + cpumask_andnot(cpus, cpus, sched_domain_span(sd)); > + } > + > + return -1; > +} > +#else > +static inline int scan_cluster(struct task_struct *p, struct cpumask *cpus, > + int target, int *nr) > +{ > + return -1; > +} > +#endif > + > /* > * Scan the LLC domain for idle CPUs; this is dynamically regulated by > * comparing the average scan cost (tracked in sd->avg_scan_cost) against the > @@ -6383,6 +6417,10 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool > } > } > > + idle_cpu = scan_cluster(p, cpus, target, &nr); > + if ((unsigned int)idle_cpu < nr_cpumask_bits) > + return idle_cpu; > + > for_each_cpu_wrap(cpu, cpus, target + 1) { > if (has_idle_core) { > i = select_idle_core(p, cpu, cpus, &idle_cpu); > @@ -6390,7 +6428,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool > return i; > > } else { > - if (!--nr) > + if (--nr <= 0) > return -1; > idle_cpu = __select_idle_cpu(cpu, p); > if ((unsigned int)idle_cpu < nr_cpumask_bits) > @@ -6489,7 +6527,7 @@ 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_lowest_cache(prev, target) && > (available_idle_cpu(prev) || sched_idle_cpu(prev)) && > asym_fits_capacity(task_util, prev)) > return prev; > @@ -6515,7 +6553,7 @@ 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_lowest_cache(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)) { >
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index f80ae86bb404..dff5dec0d792 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6323,6 +6323,40 @@ static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd #endif /* CONFIG_SCHED_SMT */ +#ifdef CONFIG_SCHED_CLUSTER +/* + * Scan the cluster domain for idle CPUs and clear cluster cpumask after scanning + */ +static inline int scan_cluster(struct task_struct *p, struct cpumask *cpus, + int target, int *nr) +{ + struct sched_domain *sd = rcu_dereference(per_cpu(sd_cluster, target)); + int cpu, idle_cpu; + + /* TODO: Support SMT system with cluster topology */ + if (!sched_smt_active() && sd) { + for_each_cpu_and(cpu, cpus, sched_domain_span(sd)) { + if (!--*nr) + return -1; + + idle_cpu = __select_idle_cpu(cpu, p); + if ((unsigned int)idle_cpu < nr_cpumask_bits) + return idle_cpu; + } + + cpumask_andnot(cpus, cpus, sched_domain_span(sd)); + } + + return -1; +} +#else +static inline int scan_cluster(struct task_struct *p, struct cpumask *cpus, + int target, int *nr) +{ + return -1; +} +#endif + /* * Scan the LLC domain for idle CPUs; this is dynamically regulated by * comparing the average scan cost (tracked in sd->avg_scan_cost) against the @@ -6383,6 +6417,10 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool } } + idle_cpu = scan_cluster(p, cpus, target, &nr); + if ((unsigned int)idle_cpu < nr_cpumask_bits) + return idle_cpu; + for_each_cpu_wrap(cpu, cpus, target + 1) { if (has_idle_core) { i = select_idle_core(p, cpu, cpus, &idle_cpu); @@ -6390,7 +6428,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool return i; } else { - if (!--nr) + if (--nr <= 0) return -1; idle_cpu = __select_idle_cpu(cpu, p); if ((unsigned int)idle_cpu < nr_cpumask_bits) @@ -6489,7 +6527,7 @@ 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_lowest_cache(prev, target) && (available_idle_cpu(prev) || sched_idle_cpu(prev)) && asym_fits_capacity(task_util, prev)) return prev; @@ -6515,7 +6553,7 @@ 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_lowest_cache(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)) {