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SubjectRe: [PATCH] drm/sched: Extend the documentation.
On Thu, Apr 5, 2018 at 3:44 PM, Alex Deucher <alexdeucher@gmail.com> wrote:
> On Thu, Apr 5, 2018 at 9:41 AM, Nayan Deshmukh
> <nayan26deshmukh@gmail.com> wrote:
>> On Thu, Apr 5, 2018 at 6:59 PM, Daniel Vetter <daniel@ffwll.ch> wrote:
>>> On Thu, Apr 5, 2018 at 3:27 PM, Alex Deucher <alexdeucher@gmail.com> wrote:
>>>> On Thu, Apr 5, 2018 at 2:16 AM, Daniel Vetter <daniel@ffwll.ch> wrote:
>>>>> On Thu, Apr 5, 2018 at 12:32 AM, Eric Anholt <eric@anholt.net> wrote:
>>>>>> These comments answer all the questions I had for myself when
>>>>>> implementing a driver using the GPU scheduler.
>>>>>>
>>>>>> Signed-off-by: Eric Anholt <eric@anholt.net>
>>>>>
>>>>> Pulling all these comments into the generated kerneldoc would be
>>>>> awesome, maybe as a new "GPU Scheduler" chapter at the end of
>>>>> drm-mm.rst? Would mean a bit of busywork to convert the existing raw
>>>>> comments into proper kerneldoc. Also has the benefit that 0day will
>>>>> complain when you forget to update the comment when editing the
>>>>> function prototype - kerneldoc which isn't included anywhere in .rst
>>>>> won't be checked automatically.
>>>>
>>>> I was actually planning to do this myself, but Nayan wanted to do this
>>>> a prep work for his proposed GSoC project so I was going to see how
>>>> far he got first.
>>
>> It is still on my TODO list. Just got a bit busy with my coursework. I
>> will try to look at it during the weekend.
>
> No worries. Take your time.
>
>>>
>>> Awesome. I'm also happy to help out with any kerneldoc questions and
>>> best practices. Technically ofc no clue about the scheduler :-)
>>>
>> I was thinking of adding a different rst for scheduler altogther. Will
>> it be better to add it in drm-mm.rst itself?
>
> I had been planning to add a separate file too since it's a separate
> entity. Do whatever you think works best.

My recommendation is that to put the gist of the docs all into
source-code comments. That way there's a much higher chance to spot
them. In the docs you'll then only have the chapter structure (and not
sure the scheduler needs more than 1 chapter).

drm-mm.rst is a bit misnamed, since it contains all the stuff for
handling rendering: MM, fences, dma-buf/prime, drm_syncobjs. I think
scheduler fits very well in that topic range. We can ofc rename it to
drm-rendering.rst or similar, if the -mm.rst is misleading (plus
adjust the title).
-Daniel

>
> Alex
>
>>
>>> Cheers, Daniel
>>>> Alex
>>>>
>>>>> -Daniel
>>>>>
>>>>>> ---
>>>>>> include/drm/gpu_scheduler.h | 46 +++++++++++++++++++++++++++++++++----
>>>>>> 1 file changed, 42 insertions(+), 4 deletions(-)
>>>>>>
>>>>>> diff --git a/include/drm/gpu_scheduler.h b/include/drm/gpu_scheduler.h
>>>>>> index dfd54fb94e10..c053a32341bf 100644
>>>>>> --- a/include/drm/gpu_scheduler.h
>>>>>> +++ b/include/drm/gpu_scheduler.h
>>>>>> @@ -43,10 +43,12 @@ enum drm_sched_priority {
>>>>>> };
>>>>>>
>>>>>> /**
>>>>>> - * A scheduler entity is a wrapper around a job queue or a group
>>>>>> - * of other entities. Entities take turns emitting jobs from their
>>>>>> - * job queues to corresponding hardware ring based on scheduling
>>>>>> - * policy.
>>>>>> + * drm_sched_entity - A wrapper around a job queue (typically attached
>>>>>> + * to the DRM file_priv).
>>>>>> + *
>>>>>> + * Entities will emit jobs in order to their corresponding hardware
>>>>>> + * ring, and the scheduler will alternate between entities based on
>>>>>> + * scheduling policy.
>>>>>> */
>>>>>> struct drm_sched_entity {
>>>>>> struct list_head list;
>>>>>> @@ -78,7 +80,18 @@ struct drm_sched_rq {
>>>>>>
>>>>>> struct drm_sched_fence {
>>>>>> struct dma_fence scheduled;
>>>>>> +
>>>>>> + /* This fence is what will be signaled by the scheduler when
>>>>>> + * the job is completed.
>>>>>> + *
>>>>>> + * When setting up an out fence for the job, you should use
>>>>>> + * this, since it's available immediately upon
>>>>>> + * drm_sched_job_init(), and the fence returned by the driver
>>>>>> + * from run_job() won't be created until the dependencies have
>>>>>> + * resolved.
>>>>>> + */
>>>>>> struct dma_fence finished;
>>>>>> +
>>>>>> struct dma_fence_cb cb;
>>>>>> struct dma_fence *parent;
>>>>>> struct drm_gpu_scheduler *sched;
>>>>>> @@ -88,6 +101,13 @@ struct drm_sched_fence {
>>>>>>
>>>>>> struct drm_sched_fence *to_drm_sched_fence(struct dma_fence *f);
>>>>>>
>>>>>> +/**
>>>>>> + * drm_sched_job - A job to be run by an entity.
>>>>>> + *
>>>>>> + * A job is created by the driver using drm_sched_job_init(), and
>>>>>> + * should call drm_sched_entity_push_job() once it wants the scheduler
>>>>>> + * to schedule the job.
>>>>>> + */
>>>>>> struct drm_sched_job {
>>>>>> struct spsc_node queue_node;
>>>>>> struct drm_gpu_scheduler *sched;
>>>>>> @@ -112,10 +132,28 @@ static inline bool drm_sched_invalidate_job(struct drm_sched_job *s_job,
>>>>>> * these functions should be implemented in driver side
>>>>>> */
>>>>>> struct drm_sched_backend_ops {
>>>>>> + /* Called when the scheduler is considering scheduling this
>>>>>> + * job next, to get another struct dma_fence for this job to
>>>>>> + * block on. Once it returns NULL, run_job() may be called.
>>>>>> + */
>>>>>> struct dma_fence *(*dependency)(struct drm_sched_job *sched_job,
>>>>>> struct drm_sched_entity *s_entity);
>>>>>> +
>>>>>> + /* Called to execute the job once all of the dependencies have
>>>>>> + * been resolved. This may be called multiple times, if
>>>>>> + * timedout_job() has happened and drm_sched_job_recovery()
>>>>>> + * decides to try it again.
>>>>>> + */
>>>>>> struct dma_fence *(*run_job)(struct drm_sched_job *sched_job);
>>>>>> +
>>>>>> + /* Called when a job has taken too long to execute, to trigger
>>>>>> + * GPU recovery.
>>>>>> + */
>>>>>> void (*timedout_job)(struct drm_sched_job *sched_job);
>>>>>> +
>>>>>> + /* Called once the job's finished fence has been signaled and
>>>>>> + * it's time to clean it up.
>>>>>> + */
>>>>>> void (*free_job)(struct drm_sched_job *sched_job);
>>>>>> };
>>>>>>
>>>>>> --
>>>>>> 2.17.0
>>>>>>
>>>>>> _______________________________________________
>>>>>> dri-devel mailing list
>>>>>> dri-devel@lists.freedesktop.org
>>>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Daniel Vetter
>>>>> Software Engineer, Intel Corporation
>>>>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>>>>> _______________________________________________
>>>>> dri-devel mailing list
>>>>> dri-devel@lists.freedesktop.org
>>>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>
>>>
>>>
>>> --
>>> Daniel Vetter
>>> Software Engineer, Intel Corporation
>>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>>> _______________________________________________
>>> dri-devel mailing list
>>> dri-devel@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel



--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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