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Subject[PATCH V2] cpufreq: Call transition notifier only once for each policy
Date
Currently we call these notifiers 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 24
drivers that register for the transition notifiers today, only 5 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: Viresh Kumar <viresh.kumar@linaro.org>
---
V1->V2:
- Add cpufreq policy instead of cpus in struct cpufreq_freqs.
- Use policy->cpus instead of related_cpus everywhere in order not to
change the existing behavior.
- Merged all 7 patches into a single patch.
- Updated changlog and included Ack from David.

arch/arm/kernel/smp.c | 24 +++++++++++++++---------
arch/arm/kernel/smp_twd.c | 9 ++++++---
arch/sparc/kernel/time_64.c | 28 ++++++++++++++++------------
arch/x86/kernel/tsc.c | 32 +++++++++++++++++++++-----------
arch/x86/kvm/x86.c | 31 ++++++++++++++++++++-----------
drivers/cpufreq/cpufreq.c | 19 ++++++++++---------
include/linux/cpufreq.h | 14 +++++++-------
7 files changed, 95 insertions(+), 62 deletions(-)

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 1d6f5ea522f4..6f6b981fecda 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -758,15 +758,20 @@ 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)) {
- 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 (!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;
@@ -778,10 +783,11 @@ 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;
}
diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index b30eafeef096..495cc7282096 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -162,15 +162,18 @@ static int twd_cpufreq_transition(struct notifier_block *nb,
unsigned long state, void *data)
{
struct cpufreq_freqs *freqs = data;
+ int cpu;

/*
* The twd clock events must be reprogrammed to account for the new
* frequency. The timer is local to a cpu, so cross-call to the
* changing cpu.
*/
- if (state == CPUFREQ_POSTCHANGE)
- smp_call_function_single(freqs->cpu, twd_update_frequency,
- NULL, 1);
+ if (state != CPUFREQ_POSTCHANGE)
+ return NOTIFY_OK;
+
+ for_each_cpu(cpu, freqs->policy->cpus)
+ smp_call_function_single(cpu, twd_update_frequency, NULL, 1);

return NOTIFY_OK;
}
diff --git a/arch/sparc/kernel/time_64.c b/arch/sparc/kernel/time_64.c
index 3eb77943ce12..89fb05f90609 100644
--- a/arch/sparc/kernel/time_64.c
+++ b/arch/sparc/kernel/time_64.c
@@ -653,19 +653,23 @@ 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;

- 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,
- freq->new);
+ 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,
+ freq->new);
+ }
}

return 0;
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index 3fae23834069..cff8779fc0d2 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -956,28 +956,38 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
void *data)
{
struct cpufreq_freqs *freq = data;
- unsigned long *lpj;
-
- lpj = &boot_cpu_data.loops_per_jiffy;
-#ifdef CONFIG_SMP
- if (!(freq->flags & CPUFREQ_CONST_LOOPS))
- lpj = &cpu_data(freq->cpu).loops_per_jiffy;
-#endif
+ struct cpumask *cpus = freq->policy->cpus;
+ bool boot_cpu = !IS_ENABLED(CONFIG_SMP) || freq->flags & CPUFREQ_CONST_LOOPS;
+ unsigned long lpj;
+ int cpu;

if (!ref_freq) {
ref_freq = freq->old;
- loops_per_jiffy_ref = *lpj;
tsc_khz_ref = tsc_khz;
+
+ if (boot_cpu)
+ loops_per_jiffy_ref = boot_cpu_data.loops_per_jiffy;
+ else
+ loops_per_jiffy_ref = cpu_data(cpumask_first(cpus)).loops_per_jiffy;
}
+
if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) ||
(val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
- *lpj = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
-
+ lpj = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new);
+
if (!(freq->flags & CPUFREQ_CONST_LOOPS))
mark_tsc_unstable("cpufreq changes");

- set_cyc2ns_scale(tsc_khz, freq->cpu, rdtsc());
+ if (boot_cpu) {
+ boot_cpu_data.loops_per_jiffy = lpj;
+ } else {
+ for_each_cpu(cpu, cpus)
+ cpu_data(cpu).loops_per_jiffy = lpj;
+ }
+
+ for_each_cpu(cpu, cpus)
+ set_cyc2ns_scale(tsc_khz, cpu, rdtsc());
}

return 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 941f932373d0..653c7da11647 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6648,10 +6648,8 @@ 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;
@@ -6695,17 +6693,12 @@ 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())
@@ -6727,8 +6720,24 @@ 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;
}

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index e10922709d13..fba38bf27d26 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -300,11 +300,14 @@ 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);
@@ -324,10 +327,8 @@ 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);
- }
+ srcu_notifier_call_chain(&cpufreq_transition_notifier_list,
+ CPUFREQ_PRECHANGE, freqs);

adjust_jiffies(CPUFREQ_PRECHANGE, freqs);
break;
@@ -337,11 +338,11 @@ 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);
- srcu_notifier_call_chain(&cpufreq_transition_notifier_list,
- CPUFREQ_POSTCHANGE, freqs);
- }
+ 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;
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index b160e98076e3..e327523ddff2 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -42,13 +42,6 @@ enum cpufreq_table_sorting {
CPUFREQ_TABLE_SORTED_DESCENDING
};

-struct cpufreq_freqs {
- unsigned int cpu; /* cpu nr */
- unsigned int old;
- unsigned int new;
- u8 flags; /* flags of cpufreq_driver, see below. */
-};
-
struct cpufreq_cpuinfo {
unsigned int max_freq;
unsigned int min_freq;
@@ -156,6 +149,13 @@ struct cpufreq_policy {
struct thermal_cooling_device *cdev;
};

+struct cpufreq_freqs {
+ struct cpufreq_policy *policy;
+ unsigned int old;
+ unsigned int new;
+ u8 flags; /* flags of cpufreq_driver, see below. */
+};
+
/* Only for ACPI */
#define CPUFREQ_SHARED_TYPE_NONE (0) /* None */
#define CPUFREQ_SHARED_TYPE_HW (1) /* HW does needed coordination */
--
2.21.0.rc0.269.g1a574e7a288b
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