-----Original Message----- From: Peter Zijlstra [mailto:peterz@infradead.org] Sent: Tuesday, March 2, 2021 11:43 PM To: Song Bao Hua (Barry Song) song.bao.hua@hisilicon.com Cc: tim.c.chen@linux.intel.com; catalin.marinas@arm.com; will@kernel.org; rjw@rjwysocki.net; vincent.guittot@linaro.org; bp@alien8.de; tglx@linutronix.de; mingo@redhat.com; lenb@kernel.org; dietmar.eggemann@arm.com; rostedt@goodmis.org; bsegall@google.com; mgorman@suse.de; msys.mizuma@gmail.com; valentin.schneider@arm.com; gregkh@linuxfoundation.org; Jonathan Cameron jonathan.cameron@huawei.com; juri.lelli@redhat.com; mark.rutland@arm.com; sudeep.holla@arm.com; aubrey.li@linux.intel.com; linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; linux-acpi@vger.kernel.org; x86@kernel.org; xuwei (O) xuwei5@huawei.com; Zengtao (B) prime.zeng@hisilicon.com; guodong.xu@linaro.org; yangyicong yangyicong@huawei.com; Liguozhu (Kenneth) liguozhu@hisilicon.com; linuxarm@openeuler.org; hpa@zytor.com Subject: Re: [RFC PATCH v4 2/3] scheduler: add scheduler level for clusters
On Tue, Mar 02, 2021 at 11:59:39AM +1300, Barry Song wrote:
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 88a2e2b..d805e59 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7797,6 +7797,16 @@ int sched_cpu_activate(unsigned int cpu) if (cpumask_weight(cpu_smt_mask(cpu)) == 2) static_branch_inc_cpuslocked(&sched_smt_present); #endif
+#ifdef CONFIG_SCHED_CLUSTER
- /*
* When going up, increment the number of cluster cpus with* cluster present.*/- if (cpumask_weight(cpu_cluster_mask(cpu)) > 1)
static_branch_inc_cpuslocked(&sched_cluster_present);+#endif
set_cpu_active(cpu, true);
if (sched_smp_initialized) {
@@ -7873,6 +7883,14 @@ int sched_cpu_deactivate(unsigned int cpu) static_branch_dec_cpuslocked(&sched_smt_present); #endif
+#ifdef CONFIG_SCHED_CLUSTER
- /*
* When going down, decrement the number of cpus with cluster present.*/- if (cpumask_weight(cpu_cluster_mask(cpu)) > 1)
static_branch_dec_cpuslocked(&sched_cluster_present);+#endif
- if (!sched_smp_initialized) return 0;
I don't think that's correct. IIUC this will mean the sched_cluster_present thing will be enabled on anything with SMT (very much including x86 big cores after the next patch).
I'm thinking that at the very least you should check a CLS domain exists, but that might be hard at this point, because the sched domains haven't been build yet.
might be able to achieve the same goal by:
int cls_wt = cpumask_weight(cpu_cluster_mask(cpu)); if ((cls_wt > cpumask_weight(cpu_smt_mask(cpu))) && && (cls_wt < cpumask_weight(cpu_coregroup_mask(cpu)))) sched_cluster_present...
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 8a8bd7b..3db7b07 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6009,6 +6009,11 @@ static inline int __select_idle_cpu(int cpu) return -1; }
+#ifdef CONFIG_SCHED_CLUSTER +DEFINE_STATIC_KEY_FALSE(sched_cluster_present); +EXPORT_SYMBOL_GPL(sched_cluster_present);
I really rather think this shouldn't be exported
Ok. Make sense.
+#endif
#ifdef CONFIG_SCHED_SMT DEFINE_STATIC_KEY_FALSE(sched_smt_present); EXPORT_SYMBOL_GPL(sched_smt_present);
This is a KVM wart, it needs to know because mitigation crap.
Ok.
@@ -6116,6 +6121,26 @@ static inline int select_idle_core(struct task_struct
*p, int core, struct cpuma
#endif /* CONFIG_SCHED_SMT */
+static inline int _select_idle_cpu(bool smt, struct task_struct *p, int
target, struct cpumask *cpus, int *idle_cpu, int *nr)
+{
- int cpu, i;
- for_each_cpu_wrap(cpu, cpus, target) {
if (smt) {i = select_idle_core(p, cpu, cpus, idle_cpu);} else {if (!--*nr)return -1;i = __select_idle_cpu(cpu);}if ((unsigned int)i < nr_cpumask_bits)return i;- }
- return -1;
+}
/*
- 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
@@ -6124,7 +6149,7 @@ static inline int select_idle_core(struct task_struct
*p, int core, struct cpuma
static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd,
int target)
{ struct cpumask *cpus = this_cpu_cpumask_var_ptr(select_idle_mask);
- int i, cpu, idle_cpu = -1, nr = INT_MAX;
- int i, idle_cpu = -1, nr = INT_MAX; bool smt = test_idle_cores(target, false); int this = smp_processor_id(); struct sched_domain *this_sd;
@@ -6134,7 +6159,12 @@ static int select_idle_cpu(struct task_struct *p,
struct sched_domain *sd, int t
if (!this_sd) return -1;
- cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
- if (!sched_cluster_active())
cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);+#ifdef CONFIG_SCHED_CLUSTER
- if (sched_cluster_active())
cpumask_and(cpus, cpu_cluster_mask(target), p->cpus_ptr);+#endif
if (sched_feat(SIS_PROP) && !smt) { u64 avg_cost, avg_idle, span_avg; @@ -6155,24 +6185,32 @@ static int select_idle_cpu(struct task_struct *p,
struct sched_domain *sd, int t
time = cpu_clock(this);}
- for_each_cpu_wrap(cpu, cpus, target) {
if (smt) {i = select_idle_core(p, cpu, cpus, &idle_cpu);if ((unsigned int)i < nr_cpumask_bits)return i;
- /* scan cluster before scanning the whole llc */
+#ifdef CONFIG_SCHED_CLUSTER
- if (sched_cluster_active()) {
i = _select_idle_cpu(smt, p, target, cpus, &idle_cpu, &nr);if ((unsigned int) i < nr_cpumask_bits) {idle_cpu = i;goto done;} else if (nr <= 0)return -1;
} else {if (!--nr)return -1;idle_cpu = __select_idle_cpu(cpu);if ((unsigned int)idle_cpu < nr_cpumask_bits)break;}
cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);cpumask_andnot(cpus, cpus, cpu_cluster_mask(target));+#endif
i = _select_idle_cpu(smt, p, target, cpus, &idle_cpu, &nr);
if ((unsigned int) i < nr_cpumask_bits) {
idle_cpu = i;goto done;} else if (nr <= 0)
return -1;if (smt) set_idle_cores(this, false);
+done: if (sched_feat(SIS_PROP) && !smt) { time = cpu_clock(this) - time; update_avg(&this_sd->avg_scan_cost, time);
And this is just horrific :-(
I was actually quite struggling with this part. Had tried a couple of ways before sending this. Still the sent one was quite ugly.
Thanks Barry