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Commit 4117ebc7 authored by Robert Bragg's avatar Robert Bragg Committed by Chris Wilson
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drm/i915/perf: better pipeline aged/aging tail updates 



This updates the tail pointer race workaround handling to updating the
'aged' pointer before looking to start aging a new one. There's the
possibility that there is already new data available and so we can
immediately start aging a new pointer without having to first wait for a
later hrtimer callback (and then another to age).

Signed-off-by: default avatarRobert Bragg <robert@sixbynine.org>
Reviewed-by: default avatarMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170511154345.962-8-lionel.g.landwerlin@intel.com


Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
parent 52c57c26

drivers/gpu/drm/i915/i915_perf.c

+23 −18
Original line number Diff line number Diff line
@@ -391,6 +391,29 @@ static bool gen7_oa_buffer_check_unlocked(struct drm_i915_private *dev_priv) 


	now = ktime_get_mono_fast_ns();



	/* Update the aged tail

	 *

	 * Flip the tail pointer available for read()s once the aging tail is

	 * old enough to trust that the corresponding data will be visible to

	 * the CPU...

	 *

	 * Do this before updating the aging pointer in case we may be able to

	 * immediately start aging a new pointer too (if new data has become

	 * available) without needing to wait for a later hrtimer callback.

	 */

	if (aging_tail != INVALID_TAIL_PTR &&

	    ((now - dev_priv->perf.oa.oa_buffer.aging_timestamp) >

	     OA_TAIL_MARGIN_NSEC)) {

		aged_idx ^= 1;

		dev_priv->perf.oa.oa_buffer.aged_tail_idx = aged_idx;



		aged_tail = aging_tail;



		/* Mark that we need a new pointer to start aging... */

		dev_priv->perf.oa.oa_buffer.tails[!aged_idx].offset = INVALID_TAIL_PTR;

		aging_tail = INVALID_TAIL_PTR;

	}



	/* Update the aging tail

	 *

	 * We throttle aging tail updates until we have a new tail that
@@ -420,24 +443,6 @@ static bool gen7_oa_buffer_check_unlocked(struct drm_i915_private *dev_priv) 
		}

	}



	/* Update the aged tail

	 *

	 * Flip the tail pointer available for read()s once the aging tail is

	 * old enough to trust that the corresponding data will be visible to

	 * the CPU...

	 */

	if (aging_tail != INVALID_TAIL_PTR &&

	    ((now - dev_priv->perf.oa.oa_buffer.aging_timestamp) >

	     OA_TAIL_MARGIN_NSEC)) {

		aged_idx ^= 1;

		dev_priv->perf.oa.oa_buffer.aged_tail_idx = aged_idx;



		aged_tail = aging_tail;



		/* Mark that we need a new pointer to start aging... */

		dev_priv->perf.oa.oa_buffer.tails[!aged_idx].offset = INVALID_TAIL_PTR;

	}



	spin_unlock_irqrestore(&dev_priv->perf.oa.oa_buffer.ptr_lock, flags);



	return aged_tail == INVALID_TAIL_PTR ?