drm/v3d: Reduce the alignment of the node allocation

Currently, we are using an alignment of 128 kB to insert a node, which
ends up wasting memory as we perform plenty of small BOs allocations
(<= 4 kB). We require that allocations are aligned to 128Kb so for any
allocation smaller than that, we are wasting the difference.

This implies that we cannot effectively use the whole 4 GB address space
available for the GPU in the RPi 4. Currently, we can allocate up to
32000 BOs of 4 kB (~140 MB) and 3000 BOs of 400 kB (~1,3 GB). This can be
quite limiting for applications that have a high memory requirement, such
as vkoverhead [1].

By reducing the page alignment to 4 kB, we can allocate up to 1000000 BOs
of 4 kB (~4 GB) and 10000 BOs of 400 kB (~4 GB). Moreover, by performing
benchmarks, we were able to attest that reducing the page alignment to
4 kB can provide a general performance improvement in OpenGL
applications (e.g. glmark2).

Therefore, this patch reduces the alignment of the node allocation to 4
kB, which will allow RPi users to explore the whole 4GB virtual
address space provided by the hardware. Also, this patch allow users to
fully run vkoverhead in the RPi 4/5, solving the issue reported in [1].

[1] https://github.com/zmike/vkoverhead/issues/14

Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240923141348.2422499-8-mcanal@igalia.com

diff --git a/drivers/gpu/drm/v3d/v3d_bo.c b/drivers/gpu/drm/v3d/v3d_bo.c
index ecb80fd75b1a0e2b2ec699134dca282f850be963..427a1c405b190f104733b57ef3da1395bd51d5cd 100644 (file)
--- a/drivers/gpu/drm/v3d/v3d_bo.c
+++ b/drivers/gpu/drm/v3d/v3d_bo.c
@@ -123,7 +123,7 @@ v3d_bo_create_finish(struct drm_gem_object *obj)
         */
        ret = drm_mm_insert_node_generic(&v3d->mm, &bo->node,
                                         obj->size >> V3D_MMU_PAGE_SHIFT,
-                                        GMP_GRANULARITY >> V3D_MMU_PAGE_SHIFT, 0, 0);
+                                        SZ_4K >> V3D_MMU_PAGE_SHIFT, 0, 0);
        spin_unlock(&v3d->mm_lock);
        if (ret)
                return ret;

diff --git a/drivers/gpu/drm/v3d/v3d_drv.h b/drivers/gpu/drm/v3d/v3d_drv.h
index 41b09c8288486c04cd643b78b4cc805e2b776e92..82d6e869dd412e34228b7cca8af9e30d6fb19dc0 100644 (file)
--- a/drivers/gpu/drm/v3d/v3d_drv.h
+++ b/drivers/gpu/drm/v3d/v3d_drv.h
@@ -19,8 +19,6 @@ struct clk;
 struct platform_device;
 struct reset_control;
 
-#define GMP_GRANULARITY (128 * 1024)
-
 #define V3D_MMU_PAGE_SHIFT 12
 
 #define V3D_MAX_QUEUES (V3D_CPU + 1)