[Intel-gfx] [PATCH v5 12/35] drm/i915: Added deferred work handler for scheduler

Tue Mar 1 15:12:13 UTC 2016

On 01/03/2016 09:16, Joonas Lahtinen wrote:
> On to, 2016-02-18 at 14:27 +0000, John.C.Harrison at Intel.com wrote:
>> From: John Harrison <John.C.Harrison at Intel.com>
>>
>> The scheduler needs to do interrupt triggered work that is too complex
>> to do in the interrupt handler. Thus it requires a deferred work
>> handler to process such tasks asynchronously.
>>
>> v2: Updated to reduce mutex lock usage. The lock is now only held for
>> the minimum time within the remove function rather than for the whole
>> of the worker thread's operation.
>>
>> v5: Removed objectionable white space and added some documentation.
>> [Joonas Lahtinen]
>>
>> For: VIZ-1587
>> Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
>> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
>> ---
>>   drivers/gpu/drm/i915/i915_dma.c       |  3 +++
>>   drivers/gpu/drm/i915/i915_drv.h       | 10 ++++++++++
>>   drivers/gpu/drm/i915/i915_gem.c       |  2 ++
>>   drivers/gpu/drm/i915/i915_scheduler.c | 29 +++++++++++++++++++++++++++--
>>   drivers/gpu/drm/i915/i915_scheduler.h |  1 +
>>   5 files changed, 43 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
>> index 678adc7..c3d382d 100644
>> --- a/drivers/gpu/drm/i915/i915_dma.c
>> +++ b/drivers/gpu/drm/i915/i915_dma.c
>> @@ -1158,6 +1158,9 @@ int i915_driver_unload(struct drm_device *dev)
>>   	WARN_ON(unregister_oom_notifier(&dev_priv->mm.oom_notifier));
>>   	unregister_shrinker(&dev_priv->mm.shrinker);
>>   
>> +	/* Cancel the scheduler work handler, which should be idle now. */
>> +	cancel_work_sync(&dev_priv->mm.scheduler_work);
>> +
>>   	io_mapping_free(dev_priv->gtt.mappable);
>>   	arch_phys_wc_del(dev_priv->gtt.mtrr);
>>   
>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>> index 03add1a..4d544f1 100644
>> --- a/drivers/gpu/drm/i915/i915_drv.h
>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>> @@ -1291,6 +1291,16 @@ struct i915_gem_mm {
>>   	struct delayed_work retire_work;
>>   
>>   	/**
>> +	 * New scheme is to get an interrupt after every work packet
>> +	 * in order to allow the low latency scheduling of pending
>> +	 * packets. The idea behind adding new packets to a pending
>> +	 * queue rather than directly into the hardware ring buffer
>> +	 * is to allow high priority packets to over take low priority
>> +	 * ones.
>> +	 */
>> +	struct work_struct scheduler_work;
>> +
>> +	/**
>>   	 * When we detect an idle GPU, we want to turn on
>>   	 * powersaving features. So once we see that there
>>   	 * are no more requests outstanding and no more
>> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
>> index c3b7def..1ab7256 100644
>> --- a/drivers/gpu/drm/i915/i915_gem.c
>> +++ b/drivers/gpu/drm/i915/i915_gem.c
>> @@ -5427,6 +5427,8 @@ i915_gem_load(struct drm_device *dev)
>>   			  i915_gem_retire_work_handler);
>>   	INIT_DELAYED_WORK(&dev_priv->mm.idle_work,
>>   			  i915_gem_idle_work_handler);
>> +	INIT_WORK(&dev_priv->mm.scheduler_work,
>> +				i915_scheduler_work_handler);
>>   	init_waitqueue_head(&dev_priv->gpu_error.reset_queue);
>>   
>>   	dev_priv->relative_constants_mode = I915_EXEC_CONSTANTS_REL_GENERAL;
>> diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
>> index ab5007a..3986890 100644
>> --- a/drivers/gpu/drm/i915/i915_scheduler.c
>> +++ b/drivers/gpu/drm/i915/i915_scheduler.c
>> @@ -697,7 +697,9 @@ static int i915_scheduler_remove_dependent(struct i915_scheduler *scheduler,
>>    */
>>   void i915_scheduler_wakeup(struct drm_device *dev)
>>   {
>> -	/* XXX: Need to call i915_scheduler_remove() via work handler. */
>> +	struct drm_i915_private *dev_priv = to_i915(dev);
>> +
>> +	queue_work(dev_priv->wq, &dev_priv->mm.scheduler_work);
>>   }
>>   
>>   /**
>> @@ -827,7 +829,7 @@ static bool i915_scheduler_remove(struct i915_scheduler *scheduler,
>>   	return do_submit;
>>   }
>>   
>> -void i915_scheduler_process_work(struct intel_engine_cs *ring)
>> +static void i915_scheduler_process_work(struct intel_engine_cs *ring)
> This is an odd change, maybe should have been static void to begin
> with?
The problems of introducing code in patch A and plumbing it to the 
driver in patch B. Making it static from the start gives an unused 
function compiler warning.

>>   {
>>   	struct drm_i915_private *dev_priv = ring->dev->dev_private;
>>   	struct i915_scheduler *scheduler = dev_priv->scheduler;
>> @@ -874,6 +876,29 @@ void i915_scheduler_process_work(struct intel_engine_cs *ring)
>>   }
>>   
>>   /**
>> + * i915_scheduler_work_handler - scheduler's work handler callback.
>> + * @work: Work structure
>> + * A lot of the scheduler's work must be done asynchronously in response to
>> + * an interrupt or other event. However, that work cannot be done at
>> + * interrupt time or in the context of the event signaller (which might in
>> + * fact be an interrupt). Thus a worker thread is required. This function
>> + * will cause the thread to wake up and do its processing.
>> + */
>> +void i915_scheduler_work_handler(struct work_struct *work)
>> +{
>> +	struct intel_engine_cs *ring;
>> +	struct drm_i915_private *dev_priv;
>> +	struct drm_device *dev;
>> +	int i;
>> +
>> +	dev_priv = container_of(work, struct drm_i915_private, mm.scheduler_work);
>> +	dev = dev_priv->dev;
> dev is unused variable?
>
> With those changes,
>
> Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
>
>> +
>> +	for_each_ring(ring, dev_priv, i)
>> +		i915_scheduler_process_work(ring);
>> +}
>> +
>> +/**
>>    * i915_scheduler_closefile - notify the scheduler that a DRM file handle
>>    * has been closed.
>>    * @dev: DRM device
>> diff --git a/drivers/gpu/drm/i915/i915_scheduler.h b/drivers/gpu/drm/i915/i915_scheduler.h
>> index 0e8b6a9..180d75f 100644
>> --- a/drivers/gpu/drm/i915/i915_scheduler.h
>> +++ b/drivers/gpu/drm/i915/i915_scheduler.h
>> @@ -93,5 +93,6 @@ void i915_scheduler_clean_node(struct i915_scheduler_queue_entry *node);
>>   int i915_scheduler_queue_execbuffer(struct i915_scheduler_queue_entry *qe);
>>   bool i915_scheduler_notify_request(struct drm_i915_gem_request *req);
>>   void i915_scheduler_wakeup(struct drm_device *dev);
>> +void i915_scheduler_work_handler(struct work_struct *work);
>>   
>>   #endif  /* _I915_SCHEDULER_H_ */