Re: [PATCH 1/2] drm/i915: Align the hangcheck wakeup to the nearest second

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 05 Oct 2012, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> round_jiffies() aligns the wakeup time to the nearest second in order to
> batch wakeups and reduce system load, which is useful for unimportant
> coarse timers like our hangcheck.
>
> Suggested-by: Arjan van de Ven <arjan@linux.intel.com>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Arjan van de Ven <arjan@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h |    1 +
>  drivers/gpu/drm/i915/i915_gem.c |    3 +--
>  drivers/gpu/drm/i915/i915_irq.c |    5 ++---
>  3 files changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index d8043af..f79c664 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -460,6 +460,7 @@ typedef struct drm_i915_private {
>  
>  	/* For hangcheck timer */
>  #define DRM_I915_HANGCHECK_PERIOD 1500 /* in ms */
> +#define DRM_I915_HANGCHECK_JIFFIES msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD)
>  	struct timer_list hangcheck_timer;
>  	int hangcheck_count;
>  	uint32_t last_acthd[I915_NUM_RINGS];
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index c78f8e3..8e05d53 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2151,8 +2151,7 @@ i915_add_request(struct intel_ring_buffer *ring,
>  	if (!dev_priv->mm.suspended) {
>  		if (i915_enable_hangcheck) {
>  			mod_timer(&dev_priv->hangcheck_timer,
> -				  jiffies +
> -				  msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
> +				  round_jiffies_relative(DRM_I915_HANGCHECK_JIFFIES));

What is DRM_I915_HANGCHECK_PERIOD based on; specifically is it a strict
minimum value? Should round_jiffies_*up*_relative() be used instead?

BR,
Jani.


>  		}
>  		if (was_empty) {
>  			queue_delayed_work(dev_priv->wq,
> diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> index e18e56b..67dc487 100644
> --- a/drivers/gpu/drm/i915/i915_irq.c
> +++ b/drivers/gpu/drm/i915/i915_irq.c
> @@ -353,8 +353,7 @@ static void notify_ring(struct drm_device *dev,
>  	if (i915_enable_hangcheck) {
>  		dev_priv->hangcheck_count = 0;
>  		mod_timer(&dev_priv->hangcheck_timer,
> -			  jiffies +
> -			  msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
> +			  round_jiffies_relative(DRM_I915_HANGCHECK_JIFFIES));
>  	}
>  }
>  
> @@ -1787,7 +1786,7 @@ void i915_hangcheck_elapsed(unsigned long data)
>  repeat:
>  	/* Reset timer case chip hangs without another request being added */
>  	mod_timer(&dev_priv->hangcheck_timer,
> -		  jiffies + msecs_to_jiffies(DRM_I915_HANGCHECK_PERIOD));
> +		  round_jiffies_relative(DRM_I915_HANGCHECK_JIFFIES));
>  }
>  
>  /* drm_dma.h hooks
> -- 
> 1.7.10.4
>
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