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: Robert Bragg <rob...@sixbynine.org>
---
drivers/gpu/drm/i915/i915_perf.c | 41 ++++++++++++++++++++++------------------
1 file changed, 23 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 19d0e4222974..d04ebaa8406e 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -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 ?
--
2.11.1
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