From f749ed618e21b56a36a2feb9b4333ec797ec2ae5 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Tue, 5 Jul 2011 21:37:02 +0100
Subject: [PATCH] sna: Reduce tiling if pitch is less than a tile_width/height
 only on pre-G33

(Note this only applies to 2D pixmaps.)

The rationale, borne out by experimentation with cairo-perf-trace, is
that on the pre-G33 devices we always need a fence region region
for tiled surfaces, i.e. at least .5/1MiB in size, and that combined
with the smaller GTT on those devices, we loose the benefit of tiling to
the excessive GTT thrashing.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 src/sna/kgem.c | 44 +++++++++++++++++++++++++-------------------
 1 file changed, 25 insertions(+), 19 deletions(-)

diff --git a/src/sna/kgem.c b/src/sna/kgem.c
index 9509dbe3..87acb49b 100644
--- a/src/sna/kgem.c
+++ b/src/sna/kgem.c
@@ -1172,26 +1172,32 @@ int kgem_choose_tiling(struct kgem *kgem, int tiling, int width, int height, int
 		return -tiling;
 	}
 
-	if (tiling == I915_TILING_Y && height < 16) {
-		DBG(("%s: too short [%d] for TILING_Y\n",
-		     __FUNCTION__,height));
-		tiling = I915_TILING_X;
-	}
-	if (tiling == I915_TILING_X && height < 4) {
-		DBG(("%s: too short [%d] for TILING_X\n",
-		     __FUNCTION__, height));
-		tiling = I915_TILING_NONE;
-	}
+	/* Before the G33, we only have a small GTT to play with and tiled
+	 * surfaces always require full fence regions and so cause excessive
+	 * aperture thrashing.
+	 */
+	if (kgem->gen < 33) {
+		if (tiling == I915_TILING_Y && height < 16) {
+			DBG(("%s: too short [%d] for TILING_Y\n",
+			     __FUNCTION__,height));
+			tiling = I915_TILING_X;
+		}
+		if (tiling == I915_TILING_X && height < 4) {
+			DBG(("%s: too short [%d] for TILING_X\n",
+			     __FUNCTION__, height));
+			tiling = I915_TILING_NONE;
+		}
 
-	if (tiling == I915_TILING_X && width * bpp < 512/2) {
-		DBG(("%s: too thin [%d] for TILING_X\n",
-		     __FUNCTION__, width));
-		tiling = I915_TILING_NONE;
-	}
-	if (tiling == I915_TILING_Y && width * bpp < 32/2) {
-		DBG(("%s: too thin [%d] for TILING_Y\n",
-		     __FUNCTION__, width));
-		tiling = I915_TILING_NONE;
+		if (tiling == I915_TILING_X && width * bpp < 8*512/2) {
+			DBG(("%s: too thin [%d] for TILING_X\n",
+			     __FUNCTION__, width));
+			tiling = I915_TILING_NONE;
+		}
+		if (tiling == I915_TILING_Y && width * bpp < 8*32/2) {
+			DBG(("%s: too thin [%d] for TILING_Y\n",
+			     __FUNCTION__, width));
+			tiling = I915_TILING_NONE;
+		}
 	}
 
 	DBG(("%s: %dx%d -> %d\n", __FUNCTION__, width, height, tiling));