i830: Prevent allocation of bo larger than half the aperture

We need to prevent overcommitting the aperture, and in particular if we
allocate a buffer larger than available space we will fail to mmap it in
and rendering will fail. Trying to allocate multiple large buffers in
the aperture, often the case when falling back, causes thrashes and
eviction of useful buffers. So from the outset simply do not allocate a
bo if the the required size is more than half the available aperture
space.

Fixes allocation failure in ocitymap.trace for instance.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Owain G. Ainsworth <oga@openbsd.org>

1 files changed, 37 insertions, 35 deletions

diff --git a/src/i830_memory.c b/src/i830_memory.c
index 935575dd..353647ff 100644
--- a/src/i830_memory.c
+++ b/src/i830_memory.c
@@ -1680,53 +1680,55 @@ void i830_free_xvmc_buffer(ScrnInfoPtr scrn, i830_memory * buffer)
 
 #endif
 
-static void i830_set_max_gtt_map_size(ScrnInfoPtr scrn)
+static void i830_set_max_bo_size(intel_screen_private *intel,
+				 const struct drm_i915_gem_get_aperture *aperture)
 {
-	intel_screen_private *intel = intel_get_screen_private(scrn);
-	struct drm_i915_gem_get_aperture aperture;
-	int ret;
-
-	/* Default low value in case it gets used during server init. */
-	intel->max_gtt_map_size = 16 * 1024 * 1024;
-
-	if (!intel->have_gem)
-		return;
+	if (aperture->aper_available_size)
+		/* Large BOs will tend to hit SW fallbacks frequently, and also will
+		 * tend to fail to successfully map when doing SW fallbacks because we
+		 * overcommit address space for BO access, or worse cause aperture
+		 * thrashing.
+		 */
+		intel->max_bo_size = aperture->aper_available_size / 2;
+	else
+		intel->max_bo_size = 64 * 1024 * 1024;
+}
 
-	ret =
-	    ioctl(intel->drmSubFD, DRM_IOCTL_I915_GEM_GET_APERTURE, &aperture);
-	if (ret == 0) {
-		/* Let objects up get bound up to the size where only 2 would
-		 * fit in the aperture, but then leave slop to account for
-		 * alignment like libdrm does.
+static void i830_set_max_gtt_map_size(intel_screen_private *intel,
+				      const struct drm_i915_gem_get_aperture *aperture)
+{
+	if (aperture->aper_available_size)
+		/* Let objects up get bound up to the size where only 2 would fit in
+		 * the aperture, but then leave slop to account for alignment like
+		 * libdrm does.
 		 */
 		intel->max_gtt_map_size =
-		    aperture.aper_available_size * 3 / 4 / 2;
-	}
+			aperture->aper_available_size * 3 / 4 / 2;
+	else
+		intel->max_gtt_map_size = 16 * 1024 * 1024;
 }
 
-static void i830_set_max_tiling_size(ScrnInfoPtr scrn)
+static void i830_set_max_tiling_size(intel_screen_private *intel,
+				     const struct drm_i915_gem_get_aperture *aperture)
 {
-	intel_screen_private *intel = intel_get_screen_private(scrn);
-	struct drm_i915_gem_get_aperture aperture;
-	int ret;
-
-	/* Default low value in case it gets used during server init. */
-	intel->max_tiling_size = 4 * 1024 * 1024;
-
-	ret =
-	    ioctl(intel->drmSubFD, DRM_IOCTL_I915_GEM_GET_APERTURE, &aperture);
-	if (ret == 0) {
+	if (aperture->aper_available_size)
 		/* Let objects be tiled up to the size where only 4 would fit in
 		 * the aperture, presuming worst case alignment.
 		 */
-		intel->max_tiling_size = aperture.aper_available_size / 4;
-		if (!IS_I965G(intel))
-			intel->max_tiling_size /= 2;
-	}
+		intel->max_tiling_size = aperture->aper_available_size / 4;
+	else
+		intel->max_tiling_size = 4 * 1024 * 1024;
 }
 
 void i830_set_gem_max_sizes(ScrnInfoPtr scrn)
 {
-	i830_set_max_gtt_map_size(scrn);
-	i830_set_max_tiling_size(scrn);
+	intel_screen_private *intel = intel_get_screen_private(scrn);
+	struct drm_i915_gem_get_aperture aperture;
+
+	aperture.aper_available_size = 0;
+	ioctl(intel->drmSubFD, DRM_IOCTL_I915_GEM_GET_APERTURE, &aperture);
+
+	i830_set_max_bo_size(intel, &aperture);
+	i830_set_max_gtt_map_size(intel, &aperture);
+	i830_set_max_tiling_size(intel, &aperture);
 }