[Intel-gfx] [PATCH 1/2] drm/i915: Improve fallback ring waiting

[Daniel Vetter]

On Mon, May 05, 2014 at 09:07:32AM +0100, Chris Wilson wrote:
> A few improvements to the fallback method for waiting upon ring space:
> 
> 1. Fix the start/end wait tracepoints to always be paired.
> 2. Increase responsiveness of checking
> 3. Mark the process as waiting upon io
> 4. Check for signal interruptions
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 24 +++++++++++++++++-------
>  1 file changed, 17 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index e0c7bf27eafd..d6b7b884adf9 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -1546,7 +1546,6 @@ static int ring_wait_for_space(struct intel_ring_buffer *ring, int n)
>  	/* force the tail write in case we have been skipping them */
>  	__intel_ring_advance(ring);
>  
> -	trace_i915_ring_wait_begin(ring);
>  	/* With GEM the hangcheck timer should kick us out of the loop,
>  	 * leaving it early runs the risk of corrupting GEM state (due
>  	 * to running on almost untested codepaths). But on resume
> @@ -1554,12 +1553,13 @@ static int ring_wait_for_space(struct intel_ring_buffer *ring, int n)
>  	 * case by choosing an insanely large timeout. */
>  	end = jiffies + 60 * HZ;
>  
> +	trace_i915_ring_wait_begin(ring);
>  	do {
>  		ring->head = I915_READ_HEAD(ring);
>  		ring->space = ring_space(ring);
>  		if (ring->space >= n) {
> -			trace_i915_ring_wait_end(ring);
> -			return 0;
> +			ret = 0;
> +			break;
>  		}
>  
>  		if (!drm_core_check_feature(dev, DRIVER_MODESET) &&
> @@ -1569,15 +1569,25 @@ static int ring_wait_for_space(struct intel_ring_buffer *ring, int n)
>  				master_priv->sarea_priv->perf_boxes |= I915_BOX_WAIT;
>  		}
>  
> -		msleep(1);
> +		io_schedule_timeout(1);

This isn't exported so doesn't compile too well. I've undone this change
for now. Otherwise both patches merged.
-Daniel

> +
> +		if (dev_priv->mm.interruptible && signal_pending(current)) {
> +			ret = -ERESTARTSYS;
> +			break;
> +		}
>  
>  		ret = i915_gem_check_wedge(&dev_priv->gpu_error,
>  					   dev_priv->mm.interruptible);
>  		if (ret)
> -			return ret;
> -	} while (!time_after(jiffies, end));
> +			break;
> +
> +		if (time_after(jiffies, end)) {
> +			ret = -EBUSY;
> +			break;
> +		}
> +	} while (1);
>  	trace_i915_ring_wait_end(ring);
> -	return -EBUSY;
> +	return ret;
>  }
>  
>  static int intel_wrap_ring_buffer(struct intel_ring_buffer *ring)
> -- 
> 2.0.0.rc0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch