user/sven/linux.git/drivers/gpu/buddy.c, branch next/master

drm/buddy: Improve offset-aligned allocation handling

2026-03-09T07:06:10Z

Large alignment requests previously forced the buddy allocator to search by alignment order, which often caused higher-order free blocks to be split even when a suitably aligned smaller region already existed within them. This led to excessive fragmentation, especially for workloads requesting small sizes with large alignment constraints. This change prioritizes the requested allocation size during the search and uses an augmented RB-tree field (subtree_max_alignment) to efficiently locate free blocks that satisfy both size and offset-alignment requirements. As a result, the allocator can directly select an aligned sub-region without splitting larger blocks unnecessarily. A practical example is the VKCTS test dEQP-VK.memory.allocation.basic.size_8KiB.reverse.count_4000, which repeatedly allocates 8 KiB buffers with a 256 KiB alignment. Previously, such allocations caused large blocks to be split aggressively, despite smaller aligned regions being sufficient. With this change, those aligned regions are reused directly, significantly reducing fragmentation. This improvement is visible in the amdgpu VRAM buddy allocator state (/sys/kernel/debug/dri/1/amdgpu_vram_mm). After the change, higher-order blocks are preserved and the number of low-order fragments is substantially reduced. Before: order- 5 free: 1936 MiB, blocks: 15490 order- 4 free: 967 MiB, blocks: 15486 order- 3 free: 483 MiB, blocks: 15485 order- 2 free: 241 MiB, blocks: 15486 order- 1 free: 241 MiB, blocks: 30948 After: order- 5 free: 493 MiB, blocks: 3941 order- 4 free: 246 MiB, blocks: 3943 order- 3 free: 123 MiB, blocks: 4101 order- 2 free: 61 MiB, blocks: 4101 order- 1 free: 61 MiB, blocks: 8018 By avoiding unnecessary splits, this change improves allocator efficiency and helps maintain larger contiguous free regions under heavy offset-aligned allocation workloads. v2:(Matthew) - Update augmented information along the path to the inserted node. v3: - Move the patch to gpu/buddy.c file. v4:(Matthew) - Use the helper instead of calling _ffs directly - Remove gpu_buddy_block_order(block) >= order check and drop order - Drop !node check as all callers handle this already - Return larger than any other possible alignment for __ffs64(0) - Replace __ffs with __ffs64 v5:(Matthew) - Drop subtree_max_alignment initialization at gpu_block_alloc() Signed-off-by: Arunpravin Paneer Selvam Suggested-by: Christian König Reviewed-by: Matthew Auld Link: https://patch.msgid.link/20260306060155.2114-1-Arunpravin.PaneerSelvam@amd.com

gpu/buddy: Introduce gpu_buddy_assert() for kunit-aware assertions

2026-03-03T08:07:42Z

Introduce gpu_buddy_assert(), a small helper that wraps WARN_ON() and, when CONFIG_KUNIT is enabled, also calls kunit_fail_current_test() so that any active KUnit test is marked as failed. In non-KUnit builds the macro reduces to WARN_ON(), preserving existing behaviour. Stringify the asserted condition in the failure message to make it easy to identify which assertion fired. Leave the WARN_ON() in gpu_buddy_block_trim() unchanged, as it returns -EINVAL and the caller already observes the failure via the return code. Cc: Christian König Cc: Arunpravin Paneer Selvam Suggested-by: Matthew Auld Signed-off-by: Sanjay Yadav Reviewed-by: Arunpravin Paneer Selvam Signed-off-by: Arunpravin Paneer Selvam Link: https://patch.msgid.link/20260227130037.53615-2-sanjay.kumar.yadav@intel.com

drm/buddy: Move internal helpers to buddy.c

2026-02-23T06:51:05Z

Move gpu_buddy_block_state(), gpu_buddy_block_is_allocated(), and gpu_buddy_block_is_split() from gpu_buddy.h to gpu_buddy.c as static functions since they have no external callers. Remove gpu_get_buddy() as it was an unused exported wrapper around the internal __get_buddy(). No functional changes. v2: - Rebased after DRM buddy allocator moved to drivers/gpu/ - Keep gpu_buddy_block_is_free() in header since it's now used by drm_buddy.c - Updated commit message Cc: Christian König Cc: Arunpravin Paneer Selvam Suggested-by: Matthew Auld Signed-off-by: Sanjay Yadav Reviewed-by: Arunpravin Paneer Selvam Signed-off-by: Arunpravin Paneer Selvam Link: https://patch.msgid.link/20260212092527.718455-6-sanjay.kumar.yadav@intel.com

gpu: Move DRM buddy allocator one level up (part two)

2026-02-06T01:38:35Z

Move the DRM buddy allocator one level up so that it can be used by GPU drivers (example, nova-core) that have usecases other than DRM (such as VFIO vGPU support). Modify the API, structures and Kconfigs to use "gpu_buddy" terminology. Adapt the drivers and tests to use the new API. The commit cannot be split due to bisectability, however no functional change is intended. Verified by running K-UNIT tests and build tested various configurations. Signed-off-by: Joel Fernandes Reviewed-by: Dave Airlie [airlied: I've split this into two so git can find copies easier. I've also just nuked drm_random library, that stuff needs to be done elsewhere and only the buddy tests seem to be using it]. Signed-off-by: Dave Airlie

gpu: Move DRM buddy allocator one level up (part one)

2026-02-06T01:34:02Z