Commit df24014a authored by Viresh Kumar's avatar Viresh Kumar Committed by Rafael J. Wysocki
Browse files

cpufreq: Call transition notifier only once for each policy 



Currently, the notifiers are called once for each CPU of the policy->cpus
cpumask. It would be more optimal if the notifier can be called only
once and all the relevant information be provided to it. Out of the 23
drivers that register for the transition notifiers today, only 4 of them
do per-cpu updates and the callback for the rest can be called only once
for the policy without any impact.

This would also avoid multiple function calls to the notifier callbacks
and reduce multiple iterations of notifier core's code (which does
locking as well).

This patch adds pointer to the cpufreq policy to the struct
cpufreq_freqs, so the notifier callback has all the information
available to it with a single call. The five drivers which perform
per-cpu updates are updated to use the cpufreq policy. The freqs->cpu
field is redundant now and is removed.

Acked-by: David S. Miller <davem@davemloft.net> (sparc)
Signed-off-by: default avatarViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 8f5e823f

arch/arm/kernel/smp.c

+15 −9
Original line number Diff line number Diff line
@@ -754,15 +754,20 @@ static int cpufreq_callback(struct notifier_block *nb, 
					unsigned long val, void *data)

{

	struct cpufreq_freqs *freq = data;

	int cpu = freq->cpu;

	struct cpumask *cpus = freq->policy->cpus;

	int cpu, first = cpumask_first(cpus);

	unsigned int lpj;



	if (freq->flags & CPUFREQ_CONST_LOOPS)

		return NOTIFY_OK;



	if (!per_cpu(l_p_j_ref, cpu)) {

	if (!per_cpu(l_p_j_ref, first)) {

		for_each_cpu(cpu, cpus) {

			per_cpu(l_p_j_ref, cpu) =

				per_cpu(cpu_data, cpu).loops_per_jiffy;

			per_cpu(l_p_j_ref_freq, cpu) = freq->old;

		}



		if (!global_l_p_j_ref) {

			global_l_p_j_ref = loops_per_jiffy;

			global_l_p_j_ref_freq = freq->old;
@@ -774,10 +779,11 @@ static int cpufreq_callback(struct notifier_block *nb, 
		loops_per_jiffy = cpufreq_scale(global_l_p_j_ref,

						global_l_p_j_ref_freq,

						freq->new);

		per_cpu(cpu_data, cpu).loops_per_jiffy =

			cpufreq_scale(per_cpu(l_p_j_ref, cpu),

					per_cpu(l_p_j_ref_freq, cpu),

					freq->new);



		lpj = cpufreq_scale(per_cpu(l_p_j_ref, first),

				    per_cpu(l_p_j_ref_freq, first), freq->new);

		for_each_cpu(cpu, cpus)

			per_cpu(cpu_data, cpu).loops_per_jiffy = lpj;

	}

	return NOTIFY_OK;

}

arch/sparc/kernel/time_64.c

+16 −12
Original line number Diff line number Diff line
@@ -653,20 +653,24 @@ static int sparc64_cpufreq_notifier(struct notifier_block *nb, unsigned long val 
				    void *data)

{

	struct cpufreq_freqs *freq = data;

	unsigned int cpu = freq->cpu;

	struct freq_table *ft = &per_cpu(sparc64_freq_table, cpu);

	unsigned int cpu;

	struct freq_table *ft;



	for_each_cpu(cpu, freq->policy->cpus) {

		ft = &per_cpu(sparc64_freq_table, cpu);



		if (!ft->ref_freq) {

			ft->ref_freq = freq->old;

			ft->clock_tick_ref = cpu_data(cpu).clock_tick;

		}



		if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||

		    (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {

			cpu_data(cpu).clock_tick =

			cpufreq_scale(ft->clock_tick_ref,

				      ft->ref_freq,

				cpufreq_scale(ft->clock_tick_ref, ft->ref_freq,

					      freq->new);

		}

	}



	return 0;

}

arch/x86/kernel/tsc.c

+1 −1
Original line number Diff line number Diff line
@@ -979,7 +979,7 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, 
		if (!(freq->flags & CPUFREQ_CONST_LOOPS))

			mark_tsc_unstable("cpufreq changes");



		set_cyc2ns_scale(tsc_khz, freq->cpu, rdtsc());

		set_cyc2ns_scale(tsc_khz, freq->policy->cpu, rdtsc());

	}



	return 0;

arch/x86/kvm/x86.c

+20 −11
Original line number Diff line number Diff line
@@ -6698,10 +6698,8 @@ static void kvm_hyperv_tsc_notifier(void) 
}

#endif



static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long val,

				     void *data)

static void __kvmclock_cpufreq_notifier(struct cpufreq_freqs *freq, int cpu)

{

	struct cpufreq_freqs *freq = data;

	struct kvm *kvm;

	struct kvm_vcpu *vcpu;

	int i, send_ipi = 0;
@@ -6745,17 +6743,12 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va 
	 *

	 */



	if (val == CPUFREQ_PRECHANGE && freq->old > freq->new)

		return 0;

	if (val == CPUFREQ_POSTCHANGE && freq->old < freq->new)

		return 0;



	smp_call_function_single(freq->cpu, tsc_khz_changed, freq, 1);

	smp_call_function_single(cpu, tsc_khz_changed, freq, 1);



	spin_lock(&kvm_lock);

	list_for_each_entry(kvm, &vm_list, vm_list) {

		kvm_for_each_vcpu(i, vcpu, kvm) {

			if (vcpu->cpu != freq->cpu)

			if (vcpu->cpu != cpu)

				continue;

			kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);

			if (vcpu->cpu != smp_processor_id())
@@ -6777,8 +6770,24 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va 
		 * guest context is entered kvmclock will be updated,

		 * so the guest will not see stale values.

		 */

		smp_call_function_single(freq->cpu, tsc_khz_changed, freq, 1);

		smp_call_function_single(cpu, tsc_khz_changed, freq, 1);

	}

}



static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long val,

				     void *data)

{

	struct cpufreq_freqs *freq = data;

	int cpu;



	if (val == CPUFREQ_PRECHANGE && freq->old > freq->new)

		return 0;

	if (val == CPUFREQ_POSTCHANGE && freq->old < freq->new)

		return 0;



	for_each_cpu(cpu, freq->policy->cpus)

		__kvmclock_cpufreq_notifier(freq, cpu);



	return 0;

}

drivers/cpufreq/cpufreq.c

+10 −9
Original line number Diff line number Diff line
@@ -340,11 +340,14 @@ static void cpufreq_notify_transition(struct cpufreq_policy *policy, 
				      struct cpufreq_freqs *freqs,

				      unsigned int state)

{

	int cpu;



	BUG_ON(irqs_disabled());



	if (cpufreq_disabled())

		return;



	freqs->policy = policy;

	freqs->flags = cpufreq_driver->flags;

	pr_debug("notification %u of frequency transition to %u kHz\n",

		 state, freqs->new);
@@ -364,10 +367,8 @@ static void cpufreq_notify_transition(struct cpufreq_policy *policy, 
			}

		}



		for_each_cpu(freqs->cpu, policy->cpus) {

		srcu_notifier_call_chain(&cpufreq_transition_notifier_list,

					 CPUFREQ_PRECHANGE, freqs);

		}



		adjust_jiffies(CPUFREQ_PRECHANGE, freqs);

		break;
@@ -377,11 +378,11 @@ static void cpufreq_notify_transition(struct cpufreq_policy *policy, 
		pr_debug("FREQ: %u - CPUs: %*pbl\n", freqs->new,

			 cpumask_pr_args(policy->cpus));



		for_each_cpu(freqs->cpu, policy->cpus) {

			trace_cpu_frequency(freqs->new, freqs->cpu);

		for_each_cpu(cpu, policy->cpus)

			trace_cpu_frequency(freqs->new, cpu);



		srcu_notifier_call_chain(&cpufreq_transition_notifier_list,

					 CPUFREQ_POSTCHANGE, freqs);

		}



		cpufreq_stats_record_transition(policy, freqs->new);

		policy->cur = freqs->new;

CRA Git | Maintained and supported by SUSTech CRA and CCSE