Provide to the scheduler a feedback about the temporary max available
capacity. Unlike arch_update_thermal_pressure, this doesn't need to be
filtered as the pressure will happen for dozens ms or more.
Signed-off-by: Vincent Guittot <[email protected]>
---
drivers/cpufreq/cpufreq.c | 48 +++++++++++++++++++++++++++++++++++++++
include/linux/cpufreq.h | 10 ++++++++
2 files changed, 58 insertions(+)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 44db4f59c4cc..7d5f71be8d29 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -2563,6 +2563,50 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
}
EXPORT_SYMBOL(cpufreq_get_policy);
+DEFINE_PER_CPU(unsigned long, cpufreq_pressure);
+EXPORT_PER_CPU_SYMBOL_GPL(cpufreq_pressure);
+
+/**
+ * cpufreq_update_pressure() - Update cpufreq pressure for CPUs
+ * @cpus : The related CPUs for which max capacity has been reduced
+ * @capped_freq : The maximum allowed frequency that CPUs can run at
+ *
+ * Update the value of cpufreq pressure for all @cpus in the mask. The
+ * cpumask should include all (online+offline) affected CPUs, to avoid
+ * operating on stale data when hot-plug is used for some CPUs. The
+ * @capped_freq reflects the currently allowed max CPUs frequency due to
+ * freq_qos capping. It might be also a boost frequency value, which is bigger
+ * than the internal 'capacity_freq_ref' max frequency. In such case the
+ * pressure value should simply be removed, since this is an indication that
+ * there is no capping. The @capped_freq must be provided in kHz.
+ */
+static void cpufreq_update_pressure(const struct cpumask *cpus,
+ unsigned long capped_freq)
+{
+ unsigned long max_capacity, capacity, pressure;
+ u32 max_freq;
+ int cpu;
+
+ cpu = cpumask_first(cpus);
+ max_capacity = arch_scale_cpu_capacity(cpu);
+ max_freq = arch_scale_freq_ref(cpu);
+
+ /*
+ * Handle properly the boost frequencies, which should simply clean
+ * the thermal pressure value.
+ */
+ if (max_freq <= capped_freq)
+ capacity = max_capacity;
+ else
+ capacity = mult_frac(max_capacity, capped_freq, max_freq);
+
+ pressure = max_capacity - capacity;
+
+
+ for_each_cpu(cpu, cpus)
+ WRITE_ONCE(per_cpu(cpufreq_pressure, cpu), pressure);
+}
+
/**
* cpufreq_set_policy - Modify cpufreq policy parameters.
* @policy: Policy object to modify.
@@ -2584,6 +2628,7 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
{
struct cpufreq_policy_data new_data;
struct cpufreq_governor *old_gov;
+ struct cpumask *cpus;
int ret;
memcpy(&new_data.cpuinfo, &policy->cpuinfo, sizeof(policy->cpuinfo));
@@ -2618,6 +2663,9 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
policy->max = __resolve_freq(policy, policy->max, CPUFREQ_RELATION_H);
trace_cpu_frequency_limits(policy);
+ cpus = policy->related_cpus;
+ cpufreq_update_pressure(cpus, policy->max);
+
policy->cached_target_freq = UINT_MAX;
pr_debug("new min and max freqs are %u - %u kHz\n",
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index afda5f24d3dd..b1d97edd3253 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -241,6 +241,12 @@ struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy);
void cpufreq_enable_fast_switch(struct cpufreq_policy *policy);
void cpufreq_disable_fast_switch(struct cpufreq_policy *policy);
bool has_target_index(void);
+
+DECLARE_PER_CPU(unsigned long, cpufreq_pressure);
+static inline unsigned long cpufreq_get_pressure(int cpu)
+{
+ return per_cpu(cpufreq_pressure, cpu);
+}
#else
static inline unsigned int cpufreq_get(unsigned int cpu)
{
@@ -263,6 +269,10 @@ static inline bool cpufreq_supports_freq_invariance(void)
return false;
}
static inline void disable_cpufreq(void) { }
+static inline unsigned long cpufreq_get_pressure(int cpu)
+{
+ return 0;
+}
#endif
#ifdef CONFIG_CPU_FREQ_STAT
--
2.34.1
On 12-12-23, 15:27, Vincent Guittot wrote:
> Provide to the scheduler a feedback about the temporary max available
> capacity. Unlike arch_update_thermal_pressure, this doesn't need to be
> filtered as the pressure will happen for dozens ms or more.
>
> Signed-off-by: Vincent Guittot <[email protected]>
> ---
> drivers/cpufreq/cpufreq.c | 48 +++++++++++++++++++++++++++++++++++++++
> include/linux/cpufreq.h | 10 ++++++++
> 2 files changed, 58 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 44db4f59c4cc..7d5f71be8d29 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2563,6 +2563,50 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
> }
> EXPORT_SYMBOL(cpufreq_get_policy);
>
> +DEFINE_PER_CPU(unsigned long, cpufreq_pressure);
> +EXPORT_PER_CPU_SYMBOL_GPL(cpufreq_pressure);
> +
> +/**
> + * cpufreq_update_pressure() - Update cpufreq pressure for CPUs
> + * @cpus : The related CPUs for which max capacity has been reduced
> + * @capped_freq : The maximum allowed frequency that CPUs can run at
> + *
> + * Update the value of cpufreq pressure for all @cpus in the mask. The
> + * cpumask should include all (online+offline) affected CPUs, to avoid
> + * operating on stale data when hot-plug is used for some CPUs. The
> + * @capped_freq reflects the currently allowed max CPUs frequency due to
> + * freq_qos capping. It might be also a boost frequency value, which is bigger
> + * than the internal 'capacity_freq_ref' max frequency. In such case the
> + * pressure value should simply be removed, since this is an indication that
> + * there is no capping. The @capped_freq must be provided in kHz.
> + */
> +static void cpufreq_update_pressure(const struct cpumask *cpus,
Since this is defined as 'static', why not just pass policy here ?
> + unsigned long capped_freq)
> +{
> + unsigned long max_capacity, capacity, pressure;
> + u32 max_freq;
> + int cpu;
> +
> + cpu = cpumask_first(cpus);
> + max_capacity = arch_scale_cpu_capacity(cpu);
This anyway expects all of them to be from the same policy ..
> + max_freq = arch_scale_freq_ref(cpu);
> +
> + /*
> + * Handle properly the boost frequencies, which should simply clean
> + * the thermal pressure value.
> + */
> + if (max_freq <= capped_freq)
> + capacity = max_capacity;
> + else
> + capacity = mult_frac(max_capacity, capped_freq, max_freq);
> +
> + pressure = max_capacity - capacity;
> +
Extra blank line here.
> +
> + for_each_cpu(cpu, cpus)
> + WRITE_ONCE(per_cpu(cpufreq_pressure, cpu), pressure);
> +}
> +
> /**
> * cpufreq_set_policy - Modify cpufreq policy parameters.
> * @policy: Policy object to modify.
> @@ -2584,6 +2628,7 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
> {
> struct cpufreq_policy_data new_data;
> struct cpufreq_governor *old_gov;
> + struct cpumask *cpus;
> int ret;
>
> memcpy(&new_data.cpuinfo, &policy->cpuinfo, sizeof(policy->cpuinfo));
> @@ -2618,6 +2663,9 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
> policy->max = __resolve_freq(policy, policy->max, CPUFREQ_RELATION_H);
> trace_cpu_frequency_limits(policy);
>
> + cpus = policy->related_cpus;
You don't need the extra variable anyway, but lets just pass policy
instead to the routine.
> + cpufreq_update_pressure(cpus, policy->max);
> +
> policy->cached_target_freq = UINT_MAX;
>
> pr_debug("new min and max freqs are %u - %u kHz\n",
> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> index afda5f24d3dd..b1d97edd3253 100644
> --- a/include/linux/cpufreq.h
> +++ b/include/linux/cpufreq.h
> @@ -241,6 +241,12 @@ struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy);
> void cpufreq_enable_fast_switch(struct cpufreq_policy *policy);
> void cpufreq_disable_fast_switch(struct cpufreq_policy *policy);
> bool has_target_index(void);
> +
> +DECLARE_PER_CPU(unsigned long, cpufreq_pressure);
> +static inline unsigned long cpufreq_get_pressure(int cpu)
> +{
> + return per_cpu(cpufreq_pressure, cpu);
> +}
> #else
> static inline unsigned int cpufreq_get(unsigned int cpu)
> {
> @@ -263,6 +269,10 @@ static inline bool cpufreq_supports_freq_invariance(void)
> return false;
> }
> static inline void disable_cpufreq(void) { }
> +static inline unsigned long cpufreq_get_pressure(int cpu)
> +{
> + return 0;
> +}
> #endif
>
> #ifdef CONFIG_CPU_FREQ_STAT
> --
> 2.34.1
--
viresh
On Wed, 13 Dec 2023 at 08:17, Viresh Kumar <[email protected]> wrote:
>
> On 12-12-23, 15:27, Vincent Guittot wrote:
> > Provide to the scheduler a feedback about the temporary max available
> > capacity. Unlike arch_update_thermal_pressure, this doesn't need to be
> > filtered as the pressure will happen for dozens ms or more.
> >
> > Signed-off-by: Vincent Guittot <[email protected]>
> > ---
> > drivers/cpufreq/cpufreq.c | 48 +++++++++++++++++++++++++++++++++++++++
> > include/linux/cpufreq.h | 10 ++++++++
> > 2 files changed, 58 insertions(+)
> >
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index 44db4f59c4cc..7d5f71be8d29 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -2563,6 +2563,50 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
> > }
> > EXPORT_SYMBOL(cpufreq_get_policy);
> >
> > +DEFINE_PER_CPU(unsigned long, cpufreq_pressure);
> > +EXPORT_PER_CPU_SYMBOL_GPL(cpufreq_pressure);
> > +
> > +/**
> > + * cpufreq_update_pressure() - Update cpufreq pressure for CPUs
> > + * @cpus : The related CPUs for which max capacity has been reduced
> > + * @capped_freq : The maximum allowed frequency that CPUs can run at
> > + *
> > + * Update the value of cpufreq pressure for all @cpus in the mask. The
> > + * cpumask should include all (online+offline) affected CPUs, to avoid
> > + * operating on stale data when hot-plug is used for some CPUs. The
> > + * @capped_freq reflects the currently allowed max CPUs frequency due to
> > + * freq_qos capping. It might be also a boost frequency value, which is bigger
> > + * than the internal 'capacity_freq_ref' max frequency. In such case the
> > + * pressure value should simply be removed, since this is an indication that
> > + * there is no capping. The @capped_freq must be provided in kHz.
> > + */
> > +static void cpufreq_update_pressure(const struct cpumask *cpus,
>
> Since this is defined as 'static', why not just pass policy here ?
Mainly because we only need the cpumask and also because this follows
the same pattern as other place like arch_topology.c
>
> > + unsigned long capped_freq)
> > +{
> > + unsigned long max_capacity, capacity, pressure;
> > + u32 max_freq;
> > + int cpu;
> > +
> > + cpu = cpumask_first(cpus);
> > + max_capacity = arch_scale_cpu_capacity(cpu);
>
> This anyway expects all of them to be from the same policy ..
>
> > + max_freq = arch_scale_freq_ref(cpu);
> > +
> > + /*
> > + * Handle properly the boost frequencies, which should simply clean
> > + * the thermal pressure value.
> > + */
> > + if (max_freq <= capped_freq)
> > + capacity = max_capacity;
> > + else
> > + capacity = mult_frac(max_capacity, capped_freq, max_freq);
> > +
> > + pressure = max_capacity - capacity;
> > +
>
> Extra blank line here.
>
> > +
> > + for_each_cpu(cpu, cpus)
> > + WRITE_ONCE(per_cpu(cpufreq_pressure, cpu), pressure);
> > +}
> > +
> > /**
> > * cpufreq_set_policy - Modify cpufreq policy parameters.
> > * @policy: Policy object to modify.
> > @@ -2584,6 +2628,7 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
> > {
> > struct cpufreq_policy_data new_data;
> > struct cpufreq_governor *old_gov;
> > + struct cpumask *cpus;
> > int ret;
> >
> > memcpy(&new_data.cpuinfo, &policy->cpuinfo, sizeof(policy->cpuinfo));
> > @@ -2618,6 +2663,9 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
> > policy->max = __resolve_freq(policy, policy->max, CPUFREQ_RELATION_H);
> > trace_cpu_frequency_limits(policy);
> >
> > + cpus = policy->related_cpus;
>
> You don't need the extra variable anyway, but lets just pass policy
> instead to the routine.
In fact I have followed what was done in cpufreq_cooling.c with
arch_update_thermal_pressure().
Will remove it
>
> > + cpufreq_update_pressure(cpus, policy->max);
> > +
> > policy->cached_target_freq = UINT_MAX;
> >
> > pr_debug("new min and max freqs are %u - %u kHz\n",
> > diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
> > index afda5f24d3dd..b1d97edd3253 100644
> > --- a/include/linux/cpufreq.h
> > +++ b/include/linux/cpufreq.h
> > @@ -241,6 +241,12 @@ struct kobject *get_governor_parent_kobj(struct cpufreq_policy *policy);
> > void cpufreq_enable_fast_switch(struct cpufreq_policy *policy);
> > void cpufreq_disable_fast_switch(struct cpufreq_policy *policy);
> > bool has_target_index(void);
> > +
> > +DECLARE_PER_CPU(unsigned long, cpufreq_pressure);
> > +static inline unsigned long cpufreq_get_pressure(int cpu)
> > +{
> > + return per_cpu(cpufreq_pressure, cpu);
> > +}
> > #else
> > static inline unsigned int cpufreq_get(unsigned int cpu)
> > {
> > @@ -263,6 +269,10 @@ static inline bool cpufreq_supports_freq_invariance(void)
> > return false;
> > }
> > static inline void disable_cpufreq(void) { }
> > +static inline unsigned long cpufreq_get_pressure(int cpu)
> > +{
> > + return 0;
> > +}
> > #endif
> >
> > #ifdef CONFIG_CPU_FREQ_STAT
> > --
> > 2.34.1
>
> --
> viresh
On Tue, 2023-12-12 at 15:27 +0100, Vincent Guittot wrote:
> Provide to the scheduler a feedback about the temporary max available
> capacity. Unlike arch_update_thermal_pressure, this doesn't need to be
> filtered as the pressure will happen for dozens ms or more.
>
> Signed-off-by: Vincent Guittot <[email protected]>
> ---
> drivers/cpufreq/cpufreq.c | 48 +++++++++++++++++++++++++++++++++++++++
> include/linux/cpufreq.h | 10 ++++++++
> 2 files changed, 58 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 44db4f59c4cc..7d5f71be8d29 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2563,6 +2563,50 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
> }
> EXPORT_SYMBOL(cpufreq_get_policy);
>
> +DEFINE_PER_CPU(unsigned long, cpufreq_pressure);
> +EXPORT_PER_CPU_SYMBOL_GPL(cpufreq_pressure);
> +
> +/**
> + * cpufreq_update_pressure() - Update cpufreq pressure for CPUs
> + * @cpus : The related CPUs for which max capacity has been reduced
> + * @capped_freq : The maximum allowed frequency that CPUs can run at
> + *
> + * Update the value of cpufreq pressure for all @cpus in the mask. The
> + * cpumask should include all (online+offline) affected CPUs, to avoid
> + * operating on stale data when hot-plug is used for some CPUs. The
> + * @capped_freq reflects the currently allowed max CPUs frequency due to
> + * freq_qos capping. It might be also a boost frequency value, which is bigger
> + * than the internal 'capacity_freq_ref' max frequency. In such case the
> + * pressure value should simply be removed, since this is an indication that
> + * there is no capping. The @capped_freq must be provided in kHz.
> + */
> +static void cpufreq_update_pressure(const struct cpumask *cpus,
> + unsigned long capped_freq)
> +{
> + unsigned long max_capacity, capacity, pressure;
> + u32 max_freq;
> + int cpu;
> +
> + cpu = cpumask_first(cpus);
> + max_capacity = arch_scale_cpu_capacity(cpu);
> + max_freq = arch_scale_freq_ref(cpu);
> +
> + /*
> + * Handle properly the boost frequencies, which should simply clean
> + * the thermal pressure value.
> + */
> + if (max_freq <= capped_freq)
> + capacity = max_capacity;
> + else
> + capacity = mult_frac(max_capacity, capped_freq, max_freq);
> +
> + pressure = max_capacity - capacity;
> +
> +
> + for_each_cpu(cpu, cpus)
> + WRITE_ONCE(per_cpu(cpufreq_pressure, cpu), pressure);
Seems like the pressure value computed from the first CPU applies to all CPU.
Will this be valid for non-homogeneous CPUs that could have different
max_freq and max_capacity?
Tim
On 13-12-23, 16:41, Tim Chen wrote:
> Seems like the pressure value computed from the first CPU applies to all CPU.
> Will this be valid for non-homogeneous CPUs that could have different
> max_freq and max_capacity?
The will be part of different cpufreq policies and so it will work
fine.
--
viresh
On 12-12-23, 15:27, Vincent Guittot wrote:
> @@ -2618,6 +2663,9 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
> policy->max = __resolve_freq(policy, policy->max, CPUFREQ_RELATION_H);
> trace_cpu_frequency_limits(policy);
>
> + cpus = policy->related_cpus;
> + cpufreq_update_pressure(cpus, policy->max);
> +
> policy->cached_target_freq = UINT_MAX;
One more question, why are you doing this from cpufreq_set_policy ? If
due to cpufreq cooling or from userspace, we end up limiting the
maximum possible frequency, will this routine always get called ?
--
viresh
On Thu, 14 Dec 2023 at 06:43, Viresh Kumar <[email protected]> wrote:
>
> On 12-12-23, 15:27, Vincent Guittot wrote:
> > @@ -2618,6 +2663,9 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
> > policy->max = __resolve_freq(policy, policy->max, CPUFREQ_RELATION_H);
> > trace_cpu_frequency_limits(policy);
> >
> > + cpus = policy->related_cpus;
> > + cpufreq_update_pressure(cpus, policy->max);
> > +
> > policy->cached_target_freq = UINT_MAX;
>
> One more question, why are you doing this from cpufreq_set_policy ? If
> due to cpufreq cooling or from userspace, we end up limiting the
> maximum possible frequency, will this routine always get called ?
Yes, any update of a FREQ_QOS_MAX ends up calling cpufreq_set_policy()
to update the policy->max
>
> --
> viresh
On 12/14/23 07:57, Vincent Guittot wrote:
> On Thu, 14 Dec 2023 at 06:43, Viresh Kumar <[email protected]> wrote:
>>
>> On 12-12-23, 15:27, Vincent Guittot wrote:
>>> @@ -2618,6 +2663,9 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
>>> policy->max = __resolve_freq(policy, policy->max, CPUFREQ_RELATION_H);
>>> trace_cpu_frequency_limits(policy);
>>>
>>> + cpus = policy->related_cpus;
>>> + cpufreq_update_pressure(cpus, policy->max);
>>> +
>>> policy->cached_target_freq = UINT_MAX;
>>
>> One more question, why are you doing this from cpufreq_set_policy ? If
>> due to cpufreq cooling or from userspace, we end up limiting the
>> maximum possible frequency, will this routine always get called ?
>
> Yes, any update of a FREQ_QOS_MAX ends up calling cpufreq_set_policy()
> to update the policy->max
>
Agree, cpufreq sysfs scaling_max_freq is also important to handle
in this new design. Currently we don't reflect that as reduced CPU
capacity in the scheduler. There was discussion when I proposed to feed
that CPU frequency reduction into thermal_pressure [1].
The same applies for the DTPM which is missing currently the proper
impact to the CPU reduced capacity in the scheduler.
IMHO any limit set into FREQ_QOS_MAX should be visible in this
new design of capacity reduction signaling.
[1] https://lore.kernel.org/lkml/[email protected]/
On 12/12/23 14:27, Vincent Guittot wrote:
> Provide to the scheduler a feedback about the temporary max available
> capacity. Unlike arch_update_thermal_pressure, this doesn't need to be
> filtered as the pressure will happen for dozens ms or more.
>
> Signed-off-by: Vincent Guittot <[email protected]>
> ---
> drivers/cpufreq/cpufreq.c | 48 +++++++++++++++++++++++++++++++++++++++
> include/linux/cpufreq.h | 10 ++++++++
> 2 files changed, 58 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 44db4f59c4cc..7d5f71be8d29 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -2563,6 +2563,50 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
> }
> EXPORT_SYMBOL(cpufreq_get_policy);
>
> +DEFINE_PER_CPU(unsigned long, cpufreq_pressure);
> +EXPORT_PER_CPU_SYMBOL_GPL(cpufreq_pressure);
Why do we export this variable when we have get/update functions?
Do we expect modules would manipulate those per-cpu variables
independently and not like we do per-cpumask in the update func.?
On Thu, Dec 14, 2023 at 10:07 AM Lukasz Luba <[email protected]> wrote:
>
> On 12/14/23 07:57, Vincent Guittot wrote:
> > On Thu, 14 Dec 2023 at 06:43, Viresh Kumar <[email protected]> wrote:
> >>
> >> On 12-12-23, 15:27, Vincent Guittot wrote:
> >>> @@ -2618,6 +2663,9 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
> >>> policy->max = __resolve_freq(policy, policy->max, CPUFREQ_RELATION_H);
> >>> trace_cpu_frequency_limits(policy);
> >>>
> >>> + cpus = policy->related_cpus;
> >>> + cpufreq_update_pressure(cpus, policy->max);
> >>> +
> >>> policy->cached_target_freq = UINT_MAX;
> >>
> >> One more question, why are you doing this from cpufreq_set_policy ? If
> >> due to cpufreq cooling or from userspace, we end up limiting the
> >> maximum possible frequency, will this routine always get called ?
> >
> > Yes, any update of a FREQ_QOS_MAX ends up calling cpufreq_set_policy()
> > to update the policy->max
> >
>
> Agree, cpufreq sysfs scaling_max_freq is also important to handle
> in this new design. Currently we don't reflect that as reduced CPU
> capacity in the scheduler. There was discussion when I proposed to feed
> that CPU frequency reduction into thermal_pressure [1].
>
> The same applies for the DTPM which is missing currently the proper
> impact to the CPU reduced capacity in the scheduler.
>
> IMHO any limit set into FREQ_QOS_MAX should be visible in this
> new design of capacity reduction signaling.
>
> [1] https://lore.kernel.org/lkml/[email protected]/
Actually, freq_qos_read_value(&policy->constraints, FREQ_QOS_MAX) will
return the requisite limit.
On 12/14/23 09:40, Rafael J. Wysocki wrote:
> On Thu, Dec 14, 2023 at 10:07 AM Lukasz Luba <[email protected]> wrote:
>>
>> On 12/14/23 07:57, Vincent Guittot wrote:
>>> On Thu, 14 Dec 2023 at 06:43, Viresh Kumar <[email protected]> wrote:
>>>>
>>>> On 12-12-23, 15:27, Vincent Guittot wrote:
>>>>> @@ -2618,6 +2663,9 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy,
>>>>> policy->max = __resolve_freq(policy, policy->max, CPUFREQ_RELATION_H);
>>>>> trace_cpu_frequency_limits(policy);
>>>>>
>>>>> + cpus = policy->related_cpus;
>>>>> + cpufreq_update_pressure(cpus, policy->max);
>>>>> +
>>>>> policy->cached_target_freq = UINT_MAX;
>>>>
>>>> One more question, why are you doing this from cpufreq_set_policy ? If
>>>> due to cpufreq cooling or from userspace, we end up limiting the
>>>> maximum possible frequency, will this routine always get called ?
>>>
>>> Yes, any update of a FREQ_QOS_MAX ends up calling cpufreq_set_policy()
>>> to update the policy->max
>>>
>>
>> Agree, cpufreq sysfs scaling_max_freq is also important to handle
>> in this new design. Currently we don't reflect that as reduced CPU
>> capacity in the scheduler. There was discussion when I proposed to feed
>> that CPU frequency reduction into thermal_pressure [1].
>>
>> The same applies for the DTPM which is missing currently the proper
>> impact to the CPU reduced capacity in the scheduler.
>>
>> IMHO any limit set into FREQ_QOS_MAX should be visible in this
>> new design of capacity reduction signaling.
>>
>> [1] https://lore.kernel.org/lkml/[email protected]/
>
> Actually, freq_qos_read_value(&policy->constraints, FREQ_QOS_MAX) will
> return the requisite limit.
Yes, but we need to translate that information from freq domain
into capacity domain and plumb ii into scheduler as stolen CPU capacity.
Ideally, w/o any 'smoothing' but just instant value.
That's the hope of this patch set re-design.
On Thu, 14 Dec 2023 at 10:20, Lukasz Luba <[email protected]> wrote:
>
>
>
> On 12/12/23 14:27, Vincent Guittot wrote:
> > Provide to the scheduler a feedback about the temporary max available
> > capacity. Unlike arch_update_thermal_pressure, this doesn't need to be
> > filtered as the pressure will happen for dozens ms or more.
> >
> > Signed-off-by: Vincent Guittot <[email protected]>
> > ---
> > drivers/cpufreq/cpufreq.c | 48 +++++++++++++++++++++++++++++++++++++++
> > include/linux/cpufreq.h | 10 ++++++++
> > 2 files changed, 58 insertions(+)
> >
> > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> > index 44db4f59c4cc..7d5f71be8d29 100644
> > --- a/drivers/cpufreq/cpufreq.c
> > +++ b/drivers/cpufreq/cpufreq.c
> > @@ -2563,6 +2563,50 @@ int cpufreq_get_policy(struct cpufreq_policy *policy, unsigned int cpu)
> > }
> > EXPORT_SYMBOL(cpufreq_get_policy);
> >
> > +DEFINE_PER_CPU(unsigned long, cpufreq_pressure);
> > +EXPORT_PER_CPU_SYMBOL_GPL(cpufreq_pressure);
>
> Why do we export this variable when we have get/update functions?
> Do we expect modules would manipulate those per-cpu variables
> independently and not like we do per-cpumask in the update func.?
No, I will remove the EXPORT_PER_CPU_SYMBOL_GPL