[Intel-gfx] [PATCH 2/2] drm/i915: add idle/busy tracepoints

[Chris Wilson]

On Fri, 18 Mar 2011 10:56:15 -0700, Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> Add trace points for when the GPU goes from idle to busy and vice-versa.
> Also trace when we start to idle the GPU and when it finally does idle
> (this could take awhile if the ring is full of commands).
> 
> Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org>
> ---
>  drivers/gpu/drm/i915/i915_drv.h         |    4 +++
>  drivers/gpu/drm/i915/i915_gem.c         |    4 +++
>  drivers/gpu/drm/i915/i915_irq.c         |    5 ++++
>  drivers/gpu/drm/i915/i915_trace.h       |   35 +++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_ringbuffer.c |    6 +++++
>  5 files changed, 54 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index c8a21ce..adff483 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -674,6 +674,10 @@ typedef struct drm_i915_private {
>  	int lvds_downclock;
>  	struct work_struct idle_work;
>  	struct timer_list idle_timer;
> +
> +	bool gpu_busy;
> +	unsigned long gpu_busy_start;
> +
>  	bool busy;
>  	u16 orig_clock;
>  	int child_dev_num;
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index ac23dcf..18534d7 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2208,6 +2208,8 @@ i915_gpu_idle(struct drm_device *dev)
>  	bool lists_empty;
>  	int ret, i;
>  
> +	trace_i915_gpu_idle_start(dev);
> +
>  	lists_empty = (list_empty(&dev_priv->mm.flushing_list) &&
>  		       list_empty(&dev_priv->mm.active_list));
>  	if (lists_empty)
> @@ -2220,6 +2222,8 @@ i915_gpu_idle(struct drm_device *dev)
>  			return ret;
>  	}
>  
> +	trace_i915_gpu_idle_end(dev);
> +
>  	return 0;
>  }
>  
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index 346dd85..0d3cc62 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -365,6 +365,11 @@ static void notify_ring(struct drm_device *dev,
>  	dev_priv->hangcheck_count = 0;
>  	mod_timer(&dev_priv->hangcheck_timer,
>  		  jiffies + msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
> +
> +	if (I915_READ_HEAD(ring) == I915_READ_TAIL(ring)) {
> +		dev_priv->gpu_busy = false;
> +		trace_i915_gpu_busy_end(dev_priv->dev);
> +	}
>  }

IRQ notifies should in fact be few and far between. I do not see how you
actually detect when the gpu goes idle should we not be waiting on a
request. So I think you need a pair of ring->irq_get/irq_put in and add
tracepoints for each ring as opposed to device! You can then have a device
busy which is the summation of active rings...
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre