[v1] thermal/idle_inject: Support 100% idle injection

[RFC][PATCH] thermal/idle_inject: Support 100% idle injection

Posted by Srinivas Pandruvada 3 years, 2 months ago

The users of idle injection framework allow 100% idle injection. For
example: thermal/cpuidle_cooling.c driver. When the ratio set to 100%,
the runtime_duration becomes zero.

In the function idle_inject_set_duration() in idle injection framework
run_duration_us == 0 is silently ignored, without any error (it is a
void function). So, the caller will assume that everything is fine and
100% idle is effective. But in reality the idle inject will be whatever
set before.

There are two options:
- The caller change their max state to 99% instead of 100% and
document that 100% is not supported by idle inject framework
- Support 100% idle support in idle inject framework

Since there are other protections via RT throttling, this framework can
allow 100% idle. The RT throttling will be activated at 95% idle by
default. The caller disabling RT throttling and injecting 100% idle,
should be aware that CPU can't be used at all.

The idle inject timer is started for (run_duration_us + idle_duration_us)
duration. Hence replace (run_duration_us && idle_duration_us) with
(run_duration_us + idle_duration_us) in the function
idle_inject_set_duration().

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---
 drivers/powercap/idle_inject.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/powercap/idle_inject.c b/drivers/powercap/idle_inject.c
index f48e71501429..4a4fe60d2563 100644
--- a/drivers/powercap/idle_inject.c
+++ b/drivers/powercap/idle_inject.c
@@ -184,7 +184,7 @@ void idle_inject_set_duration(struct idle_inject_device *ii_dev,
 			      unsigned int run_duration_us,
 			      unsigned int idle_duration_us)
 {
-	if (run_duration_us && idle_duration_us) {
+	if (run_duration_us + idle_duration_us) {
 		WRITE_ONCE(ii_dev->run_duration_us, run_duration_us);
 		WRITE_ONCE(ii_dev->idle_duration_us, idle_duration_us);
 	}
-- 
2.37.2

Re: [RFC][PATCH] thermal/idle_inject: Support 100% idle injection

Posted by Daniel Lezcano 3 years, 1 month ago

Hi Srinivas,


On 09/12/2022 02:36, Srinivas Pandruvada wrote:
> The users of idle injection framework allow 100% idle injection. For
> example: thermal/cpuidle_cooling.c driver. When the ratio set to 100%,
> the runtime_duration becomes zero.
> 
> In the function idle_inject_set_duration() in idle injection framework
> run_duration_us == 0 is silently ignored, without any error (it is a
> void function). So, the caller will assume that everything is fine and
> 100% idle is effective. But in reality the idle inject will be whatever
> set before.

Good catch

> There are two options:
> - The caller change their max state to 99% instead of 100% and
> document that 100% is not supported by idle inject framework
> - Support 100% idle support in idle inject framework

Yes, from my POV a CPU being impossible to cool down for any reason 
should end up by staying off.

> Since there are other protections via RT throttling, this framework can
> allow 100% idle. The RT throttling will be activated at 95% idle by
> default. The caller disabling RT throttling and injecting 100% idle,
> should be aware that CPU can't be used at all.

Would it make sense to write a trace in this case ?

> The idle inject timer is started for (run_duration_us + idle_duration_us)
> duration. Hence replace (run_duration_us && idle_duration_us) with
> (run_duration_us + idle_duration_us) in the function
> idle_inject_set_duration().

Sounds good to me

> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
> ---
>   drivers/powercap/idle_inject.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/powercap/idle_inject.c b/drivers/powercap/idle_inject.c
> index f48e71501429..4a4fe60d2563 100644
> --- a/drivers/powercap/idle_inject.c
> +++ b/drivers/powercap/idle_inject.c
> @@ -184,7 +184,7 @@ void idle_inject_set_duration(struct idle_inject_device *ii_dev,
>   			      unsigned int run_duration_us,
>   			      unsigned int idle_duration_us)
>   {
> -	if (run_duration_us && idle_duration_us) {
> +	if (run_duration_us + idle_duration_us) {
>   		WRITE_ONCE(ii_dev->run_duration_us, run_duration_us);
>   		WRITE_ONCE(ii_dev->idle_duration_us, idle_duration_us);
>   	}

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Re: [RFC][PATCH] thermal/idle_inject: Support 100% idle injection

Posted by srinivas pandruvada 3 years, 1 month ago

On Wed, 2022-12-21 at 14:43 +0100, Daniel Lezcano wrote:
> 
> Hi Srinivas,
> 
> 
> On 09/12/2022 02:36, Srinivas Pandruvada wrote:
> > The users of idle injection framework allow 100% idle injection.
> > For
> > example: thermal/cpuidle_cooling.c driver. When the ratio set to
> > 100%,
> > the runtime_duration becomes zero.
> > 
> > In the function idle_inject_set_duration() in idle injection
> > framework
> > run_duration_us == 0 is silently ignored, without any error (it is
> > a
> > void function). So, the caller will assume that everything is fine
> > and
> > 100% idle is effective. But in reality the idle inject will be
> > whatever
> > set before.
> 
> Good catch
> 
> > There are two options:
> > - The caller change their max state to 99% instead of 100% and
> > document that 100% is not supported by idle inject framework
> > - Support 100% idle support in idle inject framework
> 
> Yes, from my POV a CPU being impossible to cool down for any reason 
> should end up by staying off.
> 
> > Since there are other protections via RT throttling, this framework
> > can
> > allow 100% idle. The RT throttling will be activated at 95% idle by
> > default. The caller disabling RT throttling and injecting 100%
> > idle,
> > should be aware that CPU can't be used at all.
> 
> Would it make sense to write a trace in this case ?

There is one printk already:
printk_deferred_once("sched: RT throttling activated\n")

You mean we should add

trace_sched_* for this?

> 
> > The idle inject timer is started for (run_duration_us +
> > idle_duration_us)
> > duration. Hence replace (run_duration_us && idle_duration_us) with
> > (run_duration_us + idle_duration_us) in the function
> > idle_inject_set_duration().
> 
> Sounds good to me
> 
I will submit a patch for this.

Thanks,
Srinivas

> > Signed-off-by: Srinivas Pandruvada
> > <srinivas.pandruvada@linux.intel.com>
> > ---
> >   drivers/powercap/idle_inject.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/powercap/idle_inject.c
> > b/drivers/powercap/idle_inject.c
> > index f48e71501429..4a4fe60d2563 100644
> > --- a/drivers/powercap/idle_inject.c
> > +++ b/drivers/powercap/idle_inject.c
> > @@ -184,7 +184,7 @@ void idle_inject_set_duration(struct
> > idle_inject_device *ii_dev,
> >                               unsigned int run_duration_us,
> >                               unsigned int idle_duration_us)
> >   {
> > -       if (run_duration_us && idle_duration_us) {
> > +       if (run_duration_us + idle_duration_us) {
> >                 WRITE_ONCE(ii_dev->run_duration_us,
> > run_duration_us);
> >                 WRITE_ONCE(ii_dev->idle_duration_us,
> > idle_duration_us);
> >         }
>

Re: [RFC][PATCH] thermal/idle_inject: Support 100% idle injection

Posted by Daniel Lezcano 3 years, 1 month ago

On 21/12/2022 21:36, srinivas pandruvada wrote:
> On Wed, 2022-12-21 at 14:43 +0100, Daniel Lezcano wrote:
>>
>> Hi Srinivas,
>>
>>
>> On 09/12/2022 02:36, Srinivas Pandruvada wrote:
>>> The users of idle injection framework allow 100% idle injection.
>>> For
>>> example: thermal/cpuidle_cooling.c driver. When the ratio set to
>>> 100%,
>>> the runtime_duration becomes zero.
>>>
>>> In the function idle_inject_set_duration() in idle injection
>>> framework
>>> run_duration_us == 0 is silently ignored, without any error (it is
>>> a
>>> void function). So, the caller will assume that everything is fine
>>> and
>>> 100% idle is effective. But in reality the idle inject will be
>>> whatever
>>> set before.
>>
>> Good catch
>>
>>> There are two options:
>>> - The caller change their max state to 99% instead of 100% and
>>> document that 100% is not supported by idle inject framework
>>> - Support 100% idle support in idle inject framework
>>
>> Yes, from my POV a CPU being impossible to cool down for any reason
>> should end up by staying off.
>>
>>> Since there are other protections via RT throttling, this framework
>>> can
>>> allow 100% idle. The RT throttling will be activated at 95% idle by
>>> default. The caller disabling RT throttling and injecting 100%
>>> idle,
>>> should be aware that CPU can't be used at all.
>>
>> Would it make sense to write a trace in this case ?
> 
> There is one printk already:
> printk_deferred_once("sched: RT throttling activated\n")
> You mean we should add
> 
> trace_sched_* for this?


I meant the CPU is going 100% idle


>>> The idle inject timer is started for (run_duration_us +
>>> idle_duration_us)
>>> duration. Hence replace (run_duration_us && idle_duration_us) with
>>> (run_duration_us + idle_duration_us) in the function
>>> idle_inject_set_duration().
>>
>> Sounds good to me
>>
> I will submit a patch for this.
> 
> Thanks,
> Srinivas
> 
>>> Signed-off-by: Srinivas Pandruvada
>>> <srinivas.pandruvada@linux.intel.com>
>>> ---
>>>    drivers/powercap/idle_inject.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/powercap/idle_inject.c
>>> b/drivers/powercap/idle_inject.c
>>> index f48e71501429..4a4fe60d2563 100644
>>> --- a/drivers/powercap/idle_inject.c
>>> +++ b/drivers/powercap/idle_inject.c
>>> @@ -184,7 +184,7 @@ void idle_inject_set_duration(struct
>>> idle_inject_device *ii_dev,
>>>                                unsigned int run_duration_us,
>>>                                unsigned int idle_duration_us)
>>>    {
>>> -       if (run_duration_us && idle_duration_us) {
>>> +       if (run_duration_us + idle_duration_us) {
>>>                  WRITE_ONCE(ii_dev->run_duration_us,
>>> run_duration_us);
>>>                  WRITE_ONCE(ii_dev->idle_duration_us,
>>> idle_duration_us);
>>>          }
>>
> 

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