[2/2] drm/scheduler: Add a start_timeout_notify() backend function

Submitted by Sharat Masetty on Nov. 2, 2018, 10:31 a.m.

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Message ID 1541154693-29623-2-git-send-email-smasetty@codeaurora.org
State New
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Series "Series without cover letter" ( rev: 1 ) in Freedreno

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Commit Message

Sharat Masetty Nov. 2, 2018, 10:31 a.m.
Add an optional backend function op which will let the scheduler clients
know when the timeout got scheduled on the scheduler instance. This will
help drivers with multiple schedulers(one per ring) measure time spent on
the ring accurately, eventually helping with better timeout detection.

Signed-off-by: Sharat Masetty <smasetty@codeaurora.org>
---
Here is an example of how I plan to use this new function callback.

[1] https://patchwork.freedesktop.org/patch/254227/

 drivers/gpu/drm/scheduler/sched_main.c | 7 ++++++-
 include/drm/gpu_scheduler.h            | 6 ++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

--
1.9.1

Patch hide | download patch | download mbox

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index c993d10..afd461e 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -192,8 +192,13 @@  bool drm_sched_dependency_optimized(struct dma_fence* fence,
 static void drm_sched_start_timeout(struct drm_gpu_scheduler *sched)
 {
 	if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
-	    !list_empty(&sched->ring_mirror_list))
+	    !list_empty(&sched->ring_mirror_list)) {
+
 		schedule_delayed_work(&sched->work_tdr, sched->timeout);
+
+		if (sched->ops->start_timeout_notify)
+			sched->ops->start_timeout_notify(sched);
+	}
 }

 /* job_finish is called after hw fence signaled
diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
index d87b268..faf28b4 100644
--- a/include/drm/gpu_scheduler.h
+++ b/include/drm/gpu_scheduler.h
@@ -239,6 +239,12 @@  struct drm_sched_backend_ops {
          * and it's time to clean it up.
 	 */
 	void (*free_job)(struct drm_sched_job *sched_job);
+
+	/*
+	 * (Optional) Called to let the driver know that a timeout detection
+	 * timer has been started.
+	 */
+	void (*start_timeout_notify)(struct drm_gpu_scheduler *sched);
 };

 /**

Comments

Am 02.11.18 um 11:31 schrieb Sharat Masetty:
> Add an optional backend function op which will let the scheduler clients

> know when the timeout got scheduled on the scheduler instance. This will

> help drivers with multiple schedulers(one per ring) measure time spent on

> the ring accurately, eventually helping with better timeout detection.

>

> Signed-off-by: Sharat Masetty <smasetty@codeaurora.org>


Well, NAK. drm_sched_start_timeout() is called whenever the timer needs 
to run, but that doesn't mean that the timer is started (e.g. it can 
already be running).

So the callback would be called multiple times and not reflect the 
actual job run time.

Additional to that it can be racy, e.g. we can complete multiple jobs at 
a time before the timer is started again.

If you want to accurately count how much time you spend on each job/ring 
you need to do this by measuring the time inside your driver instead.

E.g. for amdgpu I would get the time first in amdgpu_job_run() and then 
again in amdgpu_job_free_cb() and calculate the difference.

Regards,
Christian.

> ---

> Here is an example of how I plan to use this new function callback.

>

> [1] https://patchwork.freedesktop.org/patch/254227/

>

>   drivers/gpu/drm/scheduler/sched_main.c | 7 ++++++-

>   include/drm/gpu_scheduler.h            | 6 ++++++

>   2 files changed, 12 insertions(+), 1 deletion(-)

>

> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c

> index c993d10..afd461e 100644

> --- a/drivers/gpu/drm/scheduler/sched_main.c

> +++ b/drivers/gpu/drm/scheduler/sched_main.c

> @@ -192,8 +192,13 @@ bool drm_sched_dependency_optimized(struct dma_fence* fence,

>   static void drm_sched_start_timeout(struct drm_gpu_scheduler *sched)

>   {

>   	if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&

> -	    !list_empty(&sched->ring_mirror_list))

> +	    !list_empty(&sched->ring_mirror_list)) {

> +

>   		schedule_delayed_work(&sched->work_tdr, sched->timeout);

> +

> +		if (sched->ops->start_timeout_notify)

> +			sched->ops->start_timeout_notify(sched);

> +	}

>   }

>

>   /* job_finish is called after hw fence signaled

> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h

> index d87b268..faf28b4 100644

> --- a/include/drm/gpu_scheduler.h

> +++ b/include/drm/gpu_scheduler.h

> @@ -239,6 +239,12 @@ struct drm_sched_backend_ops {

>            * and it's time to clean it up.

>   	 */

>   	void (*free_job)(struct drm_sched_job *sched_job);

> +

> +	/*

> +	 * (Optional) Called to let the driver know that a timeout detection

> +	 * timer has been started.

> +	 */

> +	void (*start_timeout_notify)(struct drm_gpu_scheduler *sched);

>   };

>

>   /**

> --

> 1.9.1

>
On 11/2/2018 4:09 PM, Koenig, Christian wrote:
> Am 02.11.18 um 11:31 schrieb Sharat Masetty:
>> Add an optional backend function op which will let the scheduler clients
>> know when the timeout got scheduled on the scheduler instance. This will
>> help drivers with multiple schedulers(one per ring) measure time spent on
>> the ring accurately, eventually helping with better timeout detection.
>>
>> Signed-off-by: Sharat Masetty <smasetty@codeaurora.org>
> 
> Well, NAK. drm_sched_start_timeout() is called whenever the timer needs
> to run, but that doesn't mean that the timer is started (e.g. it can
> already be running).
> 
> So the callback would be called multiple times and not reflect the
> actual job run time.
> 
> Additional to that it can be racy, e.g. we can complete multiple jobs at
> a time before the timer is started again.
> 
> If you want to accurately count how much time you spend on each job/ring
> you need to do this by measuring the time inside your driver instead.
> 
> E.g. for amdgpu I would get the time first in amdgpu_job_run() and then
> again in amdgpu_job_free_cb() and calculate the difference.
Hi Christian,

Thank you for the comments and apologies if this was confusing. All I 
want to determine(more accurately) is that when the scheduler instance 
timer of say 500 ms goes off, is if the ring(associated with the 
scheduler instance) actually spent 500 ms on the hardware - and for this 
I need to know in the driver space when the timer actually started.

In msm hardware we have ring preemption support enabled and the kernel 
driver triggers a preemption switch to a higher priority ring if there 
is work available on that ring for the GPU to work on. So in the 
presence of preemption it is possible that a lower priority ring did not 
actually get to spend the full 500 ms and this is what I am trying to 
catch with this callback.

I am *not* trying to profile per job time consumption with this.

 > Well, NAK. drm_sched_start_timeout() is called whenever the timer needs
 > to run, but that doesn't mean that the timer is started (e.g. it can
 > already be running).

Regarding the case where the timer may already be running - good point, 
but it should be easy to address the scenario. I will check the output
of schedule_delayed_work() and only call the callback(new proposed) if 
the timer was really scheduled.

In summary, when this timedout_job() callback is called, it is assumed 
that the job actually did time out from the POV of the scheduler, but 
this will not hold true with preemption switching and that is what I am 
trying to better address with this patch.

Sharat
> 
> Regards,
> Christian.
> 
>> ---
>> Here is an example of how I plan to use this new function callback.
>>
>> [1] https://patchwork.freedesktop.org/patch/254227/
>>
>>    drivers/gpu/drm/scheduler/sched_main.c | 7 ++++++-
>>    include/drm/gpu_scheduler.h            | 6 ++++++
>>    2 files changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
>> index c993d10..afd461e 100644
>> --- a/drivers/gpu/drm/scheduler/sched_main.c
>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
>> @@ -192,8 +192,13 @@ bool drm_sched_dependency_optimized(struct dma_fence* fence,
>>    static void drm_sched_start_timeout(struct drm_gpu_scheduler *sched)
>>    {
>>    	if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
>> -	    !list_empty(&sched->ring_mirror_list))
>> +	    !list_empty(&sched->ring_mirror_list)) {
>> +
>>    		schedule_delayed_work(&sched->work_tdr, sched->timeout);
>> +
>> +		if (sched->ops->start_timeout_notify)
>> +			sched->ops->start_timeout_notify(sched);
>> +	}
>>    }
>>
>>    /* job_finish is called after hw fence signaled
>> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
>> index d87b268..faf28b4 100644
>> --- a/include/drm/gpu_scheduler.h
>> +++ b/include/drm/gpu_scheduler.h
>> @@ -239,6 +239,12 @@ struct drm_sched_backend_ops {
>>             * and it's time to clean it up.
>>    	 */
>>    	void (*free_job)(struct drm_sched_job *sched_job);
>> +
>> +	/*
>> +	 * (Optional) Called to let the driver know that a timeout detection
>> +	 * timer has been started.
>> +	 */
>> +	void (*start_timeout_notify)(struct drm_gpu_scheduler *sched);
>>    };
>>
>>    /**
>> --
>> 1.9.1
>>
> 
> _______________________________________________
> Freedreno mailing list
> Freedreno@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/freedreno
>
Am 02.11.18 um 14:25 schrieb Sharat Masetty:
>

>

> On 11/2/2018 4:09 PM, Koenig, Christian wrote:

>> Am 02.11.18 um 11:31 schrieb Sharat Masetty:

>>> Add an optional backend function op which will let the scheduler 

>>> clients

>>> know when the timeout got scheduled on the scheduler instance. This 

>>> will

>>> help drivers with multiple schedulers(one per ring) measure time 

>>> spent on

>>> the ring accurately, eventually helping with better timeout detection.

>>>

>>> Signed-off-by: Sharat Masetty <smasetty@codeaurora.org>

>>

>> Well, NAK. drm_sched_start_timeout() is called whenever the timer needs

>> to run, but that doesn't mean that the timer is started (e.g. it can

>> already be running).

>>

>> So the callback would be called multiple times and not reflect the

>> actual job run time.

>>

>> Additional to that it can be racy, e.g. we can complete multiple jobs at

>> a time before the timer is started again.

>>

>> If you want to accurately count how much time you spend on each job/ring

>> you need to do this by measuring the time inside your driver instead.

>>

>> E.g. for amdgpu I would get the time first in amdgpu_job_run() and then

>> again in amdgpu_job_free_cb() and calculate the difference.

> Hi Christian,

>

> Thank you for the comments and apologies if this was confusing. All I 

> want to determine(more accurately) is that when the scheduler instance 

> timer of say 500 ms goes off, is if the ring(associated with the 

> scheduler instance) actually spent 500 ms on the hardware - and for 

> this I need to know in the driver space when the timer actually started.

>

> In msm hardware we have ring preemption support enabled and the kernel 

> driver triggers a preemption switch to a higher priority ring if there 

> is work available on that ring for the GPU to work on. So in the 

> presence of preemption it is possible that a lower priority ring did 

> not actually get to spend the full 500 ms and this is what I am trying 

> to catch with this callback.

>

> I am *not* trying to profile per job time consumption with this.

>

> > Well, NAK. drm_sched_start_timeout() is called whenever the timer needs

> > to run, but that doesn't mean that the timer is started (e.g. it can

> > already be running).

>

> Regarding the case where the timer may already be running - good 

> point, but it should be easy to address the scenario. I will check the 

> output

> of schedule_delayed_work() and only call the callback(new proposed) if 

> the timer was really scheduled.


Yeah, that should work.

>

> In summary, when this timedout_job() callback is called, it is assumed 

> that the job actually did time out from the POV of the scheduler, but 

> this will not hold true with preemption switching and that is what I 

> am trying to better address with this patch.


Mhm, so what you actually need is to suspend the timeout when the lower 
priority ring is preempted and resume it when it is started again? I 
wonder if that wouldn't be simpler.

We have support for ring preemption as well, but not implemented yet. So 
it would be nice to have something that works for everybody.

But on the other hand a callback to notify the driver that the timer 
started isn't so bad either.

Regards,
Christian.

>

> Sharat

>>

>> Regards,

>> Christian.

>>

>>> ---

>>> Here is an example of how I plan to use this new function callback.

>>>

>>> [1] https://patchwork.freedesktop.org/patch/254227/

>>>

>>>    drivers/gpu/drm/scheduler/sched_main.c | 7 ++++++-

>>>    include/drm/gpu_scheduler.h            | 6 ++++++

>>>    2 files changed, 12 insertions(+), 1 deletion(-)

>>>

>>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c 

>>> b/drivers/gpu/drm/scheduler/sched_main.c

>>> index c993d10..afd461e 100644

>>> --- a/drivers/gpu/drm/scheduler/sched_main.c

>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c

>>> @@ -192,8 +192,13 @@ bool drm_sched_dependency_optimized(struct 

>>> dma_fence* fence,

>>>    static void drm_sched_start_timeout(struct drm_gpu_scheduler *sched)

>>>    {

>>>        if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&

>>> -        !list_empty(&sched->ring_mirror_list))

>>> +        !list_empty(&sched->ring_mirror_list)) {

>>> +

>>>            schedule_delayed_work(&sched->work_tdr, sched->timeout);

>>> +

>>> +        if (sched->ops->start_timeout_notify)

>>> +            sched->ops->start_timeout_notify(sched);

>>> +    }

>>>    }

>>>

>>>    /* job_finish is called after hw fence signaled

>>> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h

>>> index d87b268..faf28b4 100644

>>> --- a/include/drm/gpu_scheduler.h

>>> +++ b/include/drm/gpu_scheduler.h

>>> @@ -239,6 +239,12 @@ struct drm_sched_backend_ops {

>>>             * and it's time to clean it up.

>>>         */

>>>        void (*free_job)(struct drm_sched_job *sched_job);

>>> +

>>> +    /*

>>> +     * (Optional) Called to let the driver know that a timeout 

>>> detection

>>> +     * timer has been started.

>>> +     */

>>> +    void (*start_timeout_notify)(struct drm_gpu_scheduler *sched);

>>>    };

>>>

>>>    /**

>>> -- 

>>> 1.9.1

>>>

>>

>> _______________________________________________

>> Freedreno mailing list

>> Freedreno@lists.freedesktop.org

>> https://lists.freedesktop.org/mailman/listinfo/freedreno

>>

>
On 11/2/2018 7:07 PM, Koenig, Christian wrote:
> Am 02.11.18 um 14:25 schrieb Sharat Masetty:
>>
>>
>> On 11/2/2018 4:09 PM, Koenig, Christian wrote:
>>> Am 02.11.18 um 11:31 schrieb Sharat Masetty:
>>>> Add an optional backend function op which will let the scheduler
>>>> clients
>>>> know when the timeout got scheduled on the scheduler instance. This
>>>> will
>>>> help drivers with multiple schedulers(one per ring) measure time
>>>> spent on
>>>> the ring accurately, eventually helping with better timeout detection.
>>>>
>>>> Signed-off-by: Sharat Masetty <smasetty@codeaurora.org>
>>>
>>> Well, NAK. drm_sched_start_timeout() is called whenever the timer needs
>>> to run, but that doesn't mean that the timer is started (e.g. it can
>>> already be running).
>>>
>>> So the callback would be called multiple times and not reflect the
>>> actual job run time.
>>>
>>> Additional to that it can be racy, e.g. we can complete multiple jobs at
>>> a time before the timer is started again.
>>>
>>> If you want to accurately count how much time you spend on each job/ring
>>> you need to do this by measuring the time inside your driver instead.
>>>
>>> E.g. for amdgpu I would get the time first in amdgpu_job_run() and then
>>> again in amdgpu_job_free_cb() and calculate the difference.
>> Hi Christian,
>>
>> Thank you for the comments and apologies if this was confusing. All I
>> want to determine(more accurately) is that when the scheduler instance
>> timer of say 500 ms goes off, is if the ring(associated with the
>> scheduler instance) actually spent 500 ms on the hardware - and for
>> this I need to know in the driver space when the timer actually started.
>>
>> In msm hardware we have ring preemption support enabled and the kernel
>> driver triggers a preemption switch to a higher priority ring if there
>> is work available on that ring for the GPU to work on. So in the
>> presence of preemption it is possible that a lower priority ring did
>> not actually get to spend the full 500 ms and this is what I am trying
>> to catch with this callback.
>>
>> I am *not* trying to profile per job time consumption with this.
>>
>>> Well, NAK. drm_sched_start_timeout() is called whenever the timer needs
>>> to run, but that doesn't mean that the timer is started (e.g. it can
>>> already be running).
>>
>> Regarding the case where the timer may already be running - good
>> point, but it should be easy to address the scenario. I will check the
>> output
>> of schedule_delayed_work() and only call the callback(new proposed) if
>> the timer was really scheduled.
> 
> Yeah, that should work.
> 
>>
>> In summary, when this timedout_job() callback is called, it is assumed
>> that the job actually did time out from the POV of the scheduler, but
>> this will not hold true with preemption switching and that is what I
>> am trying to better address with this patch.
> 
> Mhm, so what you actually need is to suspend the timeout when the lower
> priority ring is preempted and resume it when it is started again? I
> wonder if that wouldn't be simpler.
> 
> We have support for ring preemption as well, but not implemented yet. So
> it would be nice to have something that works for everybody.
> 
> But on the other hand a callback to notify the driver that the timer
> started isn't so bad either.
Hi Christian,

Yes something like a suspend timeout would be simpler for the drivers, 
but I could not find anything which does this for the delayed work or 
even for the general timers. All I could find was cancel/delete.

In lieu of this, I chose this approach. If you like it this way(proposed 
patch), then I will address the review comments and re-spin... please 
let me know.

Sharat
> 
> Regards,
> Christian.
> 
>>
>> Sharat
>>>
>>> Regards,
>>> Christian.
>>>
>>>> ---
>>>> Here is an example of how I plan to use this new function callback.
>>>>
>>>> [1] https://patchwork.freedesktop.org/patch/254227/
>>>>
>>>>     drivers/gpu/drm/scheduler/sched_main.c | 7 ++++++-
>>>>     include/drm/gpu_scheduler.h            | 6 ++++++
>>>>     2 files changed, 12 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c
>>>> b/drivers/gpu/drm/scheduler/sched_main.c
>>>> index c993d10..afd461e 100644
>>>> --- a/drivers/gpu/drm/scheduler/sched_main.c
>>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
>>>> @@ -192,8 +192,13 @@ bool drm_sched_dependency_optimized(struct
>>>> dma_fence* fence,
>>>>     static void drm_sched_start_timeout(struct drm_gpu_scheduler *sched)
>>>>     {
>>>>         if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
>>>> -        !list_empty(&sched->ring_mirror_list))
>>>> +        !list_empty(&sched->ring_mirror_list)) {
>>>> +
>>>>             schedule_delayed_work(&sched->work_tdr, sched->timeout);
>>>> +
>>>> +        if (sched->ops->start_timeout_notify)
>>>> +            sched->ops->start_timeout_notify(sched);
>>>> +    }
>>>>     }
>>>>
>>>>     /* job_finish is called after hw fence signaled
>>>> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
>>>> index d87b268..faf28b4 100644
>>>> --- a/include/drm/gpu_scheduler.h
>>>> +++ b/include/drm/gpu_scheduler.h
>>>> @@ -239,6 +239,12 @@ struct drm_sched_backend_ops {
>>>>              * and it's time to clean it up.
>>>>          */
>>>>         void (*free_job)(struct drm_sched_job *sched_job);
>>>> +
>>>> +    /*
>>>> +     * (Optional) Called to let the driver know that a timeout
>>>> detection
>>>> +     * timer has been started.
>>>> +     */
>>>> +    void (*start_timeout_notify)(struct drm_gpu_scheduler *sched);
>>>>     };
>>>>
>>>>     /**
>>>> -- 
>>>> 1.9.1
>>>>
>>>
>>> _______________________________________________
>>> Freedreno mailing list
>>> Freedreno@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/freedreno
>>>
>>
> 
> _______________________________________________
> Freedreno mailing list
> Freedreno@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/freedreno
>
[SNIP]

Am 05.11.18 um 08:55 schrieb Sharat Masetty:
> Hi Christian,

>

> Yes something like a suspend timeout would be simpler for the drivers, 

> but I could not find anything which does this for the delayed work or 

> even for the general timers. All I could find was cancel/delete.

>

> In lieu of this, I chose this approach. If you like it this 

> way(proposed patch), then I will address the review comments and 

> re-spin... please let me know.

>

> Sharat


I think I would prefer investigating into the suspend/resume approach 
for a moment.

What we can do rather easily is to use mod_delayed_work() with a larger 
timeout, e.g. like the following:

void drm_sched_suspend_timeout()
{
     mod_delayed_work(&sched->work_tdr, sched->timeout * 10);
}

void drm_sched_resume_timeout()
{
     mod_delayed_work(&sched->work_tdr, sched->timeout);
}

By looking at work_tdr.timer.expires before modifying it 
drm_sched_suspend_timeout() could also return the remaining jiffies to wait.

This way we wouldn't need to restart the timeout completely on every resume.

Regards,
Christian.