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Date: Wed, 24 Feb 2016 02:28:12 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM list <linux-pm@...r.kernel.org>
Cc: Juri Lelli <juri.lelli@....com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Viresh Kumar <viresh.kumar@...aro.org>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
Peter Zijlstra <peterz@...radead.org>,
Steve Muckle <steve.muckle@...aro.org>,
Ingo Molnar <mingo@...nel.org>
Subject: [RFC/RFT][PATCH v2 2/2] cpufreq: schedutil: Switching frequencies from interrupt context
From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Modify the ACPI cpufreq driver to provide a method for switching
CPU frequencies from interrupt context and update the cpufreq core
and the schedutil governor to use that method if available.
Introduce a new cpufreq driver callback, ->fast_switch, to be
invoked for frequency switching from interrupt context via
new helper function cpufreq_driver_fast_switch().
Modify the schedutil governor to call cpufreq_driver_fast_switch()
from its sugov_update_commit() function and avoid queuing up the
irq_work if that is successful.
Implement the ->fast_switch callback in the ACPI cpufreq driver
(with a limited coverage for the time being).
In addition to the above, cpufreq_governor_limits() is modified so
it doesn't call __cpufreq_driver_target() to enforce the new limits
immediately as they will be take into account anyway during the next
update from the scheduler.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
This actually is the first version of the $subject patch, but since it belongs
to the schedutil governor combo, I've given it the v2.
Please note that this is a prototype, so it may not be done the way I'll want
to do it finally, although ATM I don't quite see how that might be done in
a significantly different way. Ideas welcome, however.
It works on my test machine and doesn't break powertop even.
Thanks,
Rafael
---
drivers/cpufreq/acpi-cpufreq.c | 63 ++++++++++++++++++++++++++++++++++++
drivers/cpufreq/cpufreq.c | 35 ++++++++++++++++++++
drivers/cpufreq/cpufreq_governor.c | 8 ----
drivers/cpufreq/cpufreq_schedutil.c | 20 ++++++++---
include/linux/cpufreq.h | 4 ++
5 files changed, 117 insertions(+), 13 deletions(-)
Index: linux-pm/drivers/cpufreq/acpi-cpufreq.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/acpi-cpufreq.c
+++ linux-pm/drivers/cpufreq/acpi-cpufreq.c
@@ -70,6 +70,7 @@ struct acpi_cpufreq_data {
unsigned int cpu_feature;
unsigned int acpi_perf_cpu;
cpumask_var_t freqdomain_cpus;
+ void (*cpu_freq_fast_write)(u32 val);
};
/* acpi_perf_data is a pointer to percpu data. */
@@ -243,6 +244,15 @@ static unsigned extract_freq(u32 val, st
}
}
+void cpu_freq_fast_write_intel(u32 val)
+{
+ u32 lo, hi;
+
+ rdmsr(MSR_IA32_PERF_CTL, lo, hi);
+ lo = (lo & ~INTEL_MSR_RANGE) | (val & INTEL_MSR_RANGE);
+ wrmsr(MSR_IA32_PERF_CTL, lo, hi);
+}
+
struct msr_addr {
u32 reg;
};
@@ -484,6 +494,53 @@ out:
return result;
}
+unsigned int acpi_cpufreq_fast_switch(struct cpufreq_policy *policy,
+ unsigned int target_freq)
+{
+ struct acpi_cpufreq_data *data = policy->driver_data;
+ struct cpufreq_frequency_table *entry;
+ struct acpi_processor_performance *perf;
+ unsigned int uninitialized_var(next_perf_state);
+ unsigned int uninitialized_var(next_freq);
+ unsigned int best_diff;
+
+ if (!data->cpu_freq_fast_write)
+ return CPUFREQ_ENTRY_INVALID;
+
+ for (entry = data->freq_table, best_diff = UINT_MAX;
+ entry->frequency != CPUFREQ_TABLE_END; entry++) {
+ unsigned int diff, freq = entry->frequency;
+
+ if (freq == CPUFREQ_ENTRY_INVALID)
+ continue;
+
+ diff = abs(freq - target_freq);
+ if (diff >= best_diff)
+ continue;
+
+ best_diff = diff;
+ next_perf_state = entry->driver_data;
+ next_freq = freq;
+ if (best_diff == 0)
+ goto found;
+ }
+ if (best_diff == UINT_MAX)
+ return CPUFREQ_ENTRY_INVALID;
+
+ found:
+ perf = to_perf_data(data);
+ if (perf->state == next_perf_state) {
+ if (unlikely(data->resume))
+ data->resume = 0;
+ else
+ return next_freq;
+ }
+
+ data->cpu_freq_fast_write(perf->states[next_perf_state].control);
+ perf->state = next_perf_state;
+ return next_freq;
+}
+
static unsigned long
acpi_cpufreq_guess_freq(struct acpi_cpufreq_data *data, unsigned int cpu)
{
@@ -745,6 +802,7 @@ static int acpi_cpufreq_cpu_init(struct
pr_debug("HARDWARE addr space\n");
if (check_est_cpu(cpu)) {
data->cpu_feature = SYSTEM_INTEL_MSR_CAPABLE;
+ data->cpu_freq_fast_write = cpu_freq_fast_write_intel;
break;
}
if (check_amd_hwpstate_cpu(cpu)) {
@@ -760,6 +818,10 @@ static int acpi_cpufreq_cpu_init(struct
goto err_unreg;
}
+ if (acpi_pstate_strict || (policy_is_shared(policy) &&
+ policy->shared_type != CPUFREQ_SHARED_TYPE_ANY))
+ data->cpu_freq_fast_write = NULL;
+
data->freq_table = kzalloc(sizeof(*data->freq_table) *
(perf->state_count+1), GFP_KERNEL);
if (!data->freq_table) {
@@ -894,6 +956,7 @@ static struct freq_attr *acpi_cpufreq_at
static struct cpufreq_driver acpi_cpufreq_driver = {
.verify = cpufreq_generic_frequency_table_verify,
.target_index = acpi_cpufreq_target,
+ .fast_switch = acpi_cpufreq_fast_switch,
.bios_limit = acpi_processor_get_bios_limit,
.init = acpi_cpufreq_cpu_init,
.exit = acpi_cpufreq_cpu_exit,
Index: linux-pm/include/linux/cpufreq.h
===================================================================
--- linux-pm.orig/include/linux/cpufreq.h
+++ linux-pm/include/linux/cpufreq.h
@@ -271,6 +271,8 @@ struct cpufreq_driver {
unsigned int relation); /* Deprecated */
int (*target_index)(struct cpufreq_policy *policy,
unsigned int index);
+ unsigned int (*fast_switch)(struct cpufreq_policy *policy,
+ unsigned int target_freq);
/*
* Only for drivers with target_index() and CPUFREQ_ASYNC_NOTIFICATION
* unset.
@@ -485,6 +487,8 @@ struct cpufreq_governor {
};
/* Pass a target to the cpufreq driver */
+bool cpufreq_driver_fast_switch(struct cpufreq_policy *policy,
+ unsigned int target_freq);
int cpufreq_driver_target(struct cpufreq_policy *policy,
unsigned int target_freq,
unsigned int relation);
Index: linux-pm/drivers/cpufreq/cpufreq.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c
@@ -1814,6 +1814,41 @@ EXPORT_SYMBOL(cpufreq_unregister_notifie
* GOVERNORS *
*********************************************************************/
+/**
+ * cpufreq_driver_fast_switch - Carry out a fast CPU frequency switch.
+ * @policy: cpufreq policy to switch the frequency for.
+ * @target_freq: New frequency to set (may be approximate).
+ *
+ * Carry out a fast frequency switch from interrupt context.
+ *
+ * It is guaranteed that this function will never be called twice in parallel
+ * for the same policy and that it will not be called in parallel with either
+ * ->target() or ->target_index() for the same policy.
+ *
+ * If CPUFREQ_ENTRY_INVALID is returned by the driver's ->fast_switch()
+ * callback, the hardware configuration must be preserved.
+ *
+ * Return 'true' on success and 'false' on failures.
+ */
+bool cpufreq_driver_fast_switch(struct cpufreq_policy *policy,
+ unsigned int target_freq)
+{
+ if (target_freq == policy->cur)
+ return true;
+
+ if (cpufreq_driver->fast_switch) {
+ unsigned int freq;
+
+ freq = cpufreq_driver->fast_switch(policy, target_freq);
+ if (freq != CPUFREQ_ENTRY_INVALID) {
+ policy->cur = freq;
+ trace_cpu_frequency(freq, smp_processor_id());
+ return true;
+ }
+ }
+ return false;
+}
+
/* Must set freqs->new to intermediate frequency */
static int __target_intermediate(struct cpufreq_policy *policy,
struct cpufreq_freqs *freqs, int index)
Index: linux-pm/drivers/cpufreq/cpufreq_schedutil.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq_schedutil.c
+++ linux-pm/drivers/cpufreq/cpufreq_schedutil.c
@@ -83,12 +83,22 @@ static unsigned int sugov_next_freq(stru
static void sugov_update_commit(struct policy_dbs_info *policy_dbs, u64 time,
unsigned int next_freq)
{
- struct sugov_policy *sg_policy = to_sg_policy(policy_dbs);
-
- sg_policy->next_freq = next_freq;
policy_dbs->last_sample_time = time;
- policy_dbs->work_in_progress = true;
- irq_work_queue(&policy_dbs->irq_work);
+
+ if (cpufreq_driver_fast_switch(policy_dbs->policy, next_freq)) {
+ /*
+ * Restore the sample delay in case it has been set to 0
+ * from sysfs in the meantime.
+ */
+ gov_update_sample_delay(policy_dbs,
+ policy_dbs->dbs_data->sampling_rate);
+ } else {
+ struct sugov_policy *sg_policy = to_sg_policy(policy_dbs);
+
+ sg_policy->next_freq = next_freq;
+ policy_dbs->work_in_progress = true;
+ irq_work_queue(&policy_dbs->irq_work);
+ }
}
static void sugov_update_shared(struct update_util_data *data, u64 time,
Index: linux-pm/drivers/cpufreq/cpufreq_governor.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq_governor.c
+++ linux-pm/drivers/cpufreq/cpufreq_governor.c
@@ -612,16 +612,8 @@ static int cpufreq_governor_limits(struc
struct policy_dbs_info *policy_dbs = policy->governor_data;
mutex_lock(&policy_dbs->timer_mutex);
-
- if (policy->max < policy->cur)
- __cpufreq_driver_target(policy, policy->max, CPUFREQ_RELATION_H);
- else if (policy->min > policy->cur)
- __cpufreq_driver_target(policy, policy->min, CPUFREQ_RELATION_L);
-
gov_update_sample_delay(policy_dbs, 0);
-
mutex_unlock(&policy_dbs->timer_mutex);
-
return 0;
}
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