[Mesa-dev] [PATCH] radv: Change memory type order for GPUs without dedicated VRAM

[Alex Smith]

Put the uncached GTT type at a higher index than the visible VRAM type,
rather than having GTT first.

When we don't have dedicated VRAM, we don't have a non-visible VRAM
type, and the property flags for GTT and visible VRAM are identical.
According to the spec, for types with identical flags, we should give
the one with better performance a lower index.

Previously, apps which follow the spec guidance for choosing a memory
type would have picked the GTT type in preference to visible VRAM (all
Feral games will do this), and end up with lower performance.

On a Ryzen 5 2500U laptop (Raven Ridge), this improves average FPS in
the Rise of the Tomb Raider benchmark by up to ~30%. Tested a couple of
other (Feral) games and saw similar improvement on those as well.

Signed-off-by: Alex Smith <asmith at feralinteractive.com>
---
I noticed that the memory types advertised on my Raven laptop looked a
bit odd so played around with it and found this. I'm not sure if it is
actually expected that the performance difference between visible VRAM
and GTT is so large, seeing as it's not dedicated VRAM, but the results
are clear (and consistent, tested multiple times).
---
 src/amd/vulkan/radv_device.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/amd/vulkan/radv_device.c b/src/amd/vulkan/radv_device.c
index 3cf050ed220..d36ee226ebd 100644
--- a/src/amd/vulkan/radv_device.c
+++ b/src/amd/vulkan/radv_device.c
@@ -171,12 +171,11 @@ radv_physical_device_init_mem_types(struct radv_physical_device *device)
 			.heapIndex = vram_index,
 		};
 	}
-	if (gart_index >= 0) {
+	if (gart_index >= 0 && device->rad_info.has_dedicated_vram) {
 		device->mem_type_indices[type_count] = RADV_MEM_TYPE_GTT_WRITE_COMBINE;
 		device->memory_properties.memoryTypes[type_count++] = (VkMemoryType) {
 			.propertyFlags = VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT |
-			VK_MEMORY_PROPERTY_HOST_COHERENT_BIT |
-			(device->rad_info.has_dedicated_vram ? 0 : VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT),
+			VK_MEMORY_PROPERTY_HOST_COHERENT_BIT,
 			.heapIndex = gart_index,
 		};
 	}
@@ -189,6 +188,19 @@ radv_physical_device_init_mem_types(struct radv_physical_device *device)
 			.heapIndex = visible_vram_index,
 		};
 	}
+	if (gart_index >= 0 && !device->rad_info.has_dedicated_vram) {
+		/* Put GTT after visible VRAM for GPUs without dedicated VRAM
+		 * as they have identical property flags, and according to the
+		 * spec, for types with identical flags, the one with greater
+		 * performance must be given a lower index. */
+		device->mem_type_indices[type_count] = RADV_MEM_TYPE_GTT_WRITE_COMBINE;
+		device->memory_properties.memoryTypes[type_count++] = (VkMemoryType) {
+			.propertyFlags = VK_MEMORY_PROPERTY_DEVICE_LOCAL_BIT |
+			VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT |
+			VK_MEMORY_PROPERTY_HOST_COHERENT_BIT,
+			.heapIndex = gart_index,
+		};
+	}
 	if (gart_index >= 0) {
 		device->mem_type_indices[type_count] = RADV_MEM_TYPE_GTT_CACHED;
 		device->memory_properties.memoryTypes[type_count++] = (VkMemoryType) {
-- 
2.21.0