linux.git/include/linux/gpu_buddy.h, branch master

drm/gpu: Add gpu_buddy_allocated_addr_to_block helper

2026-08-06T11:28:54+00:00

Add helper with primary purpose is to efficiently trace a specific physical memory address back to its corresponding TTM buffer object. v3: - use mm->chunk_size minimum allocation granularity (Arun) v2: - %s/gpu_buddy_addr_to_block/gpu_buddy_allocated_addr_to_block(MattA) - remove clear->avail and split nodes check(MattA) - Adapt lockdep(MattB) Signed-off-by: Tejas Upadhyay Cc: Arunpravin Paneer Selvam Cc: dri-devel@lists.freedesktop.org Reviewed-by: Arunpravin Paneer Selvam Signed-off-by: Arunpravin Paneer Selvam Link: https://patch.msgid.link/20260806053624.3215216-5-tejas.upadhyay@intel.com

gpu/buddy: Track per-order used blocks with a scoreboard

2026-05-29T11:44:01+00:00

Extend the scoreboard approach from the previous commit to used blocks, so drm_buddy_print() can report per-order allocation pressure in O(1). Unlike free blocks, an allocated block can leave the allocated state through mark_free() (normal free and gpu_buddy_block_trim()) or be consumed directly by gpu_block_free() during coalescing. Both sites are guarded by gpu_buddy_block_is_allocated() and paired with the increment in mark_allocated(). v3: - Assert scoreboard is empty at fini(), as sanity check (Matthew Auld) v2: - Update after fix for use-after-free in split_block() call sites - Change goto label to out_free_used_scoreboard for clarity - Make drm_buddy_print() and gpu_buddy_print() symmetric for used and free Assisted-by: GitHub Copilot:claude-sonnet-4.6 Reviewed-by: Matthew Auld Link: https://lore.kernel.org/r/20260522092600.32818-6-francois.dugast@intel.com Signed-off-by: Francois Dugast

gpu/buddy: Track per-order free blocks with a scoreboard

2026-05-29T11:44:00+00:00

Reporting per-order free block counts in drm_buddy_print() currently requires walking all rbtrees, which is O(n) over the total number of free blocks and holds the allocator lock for the duration. This becomes expensive on large VRAM heaps with many small free fragments. Maintain a free_scoreboard[] array indexed by order instead, so that the count for any order is always available in O(1). The scoreboard is kept accurate by hooking into the four places where a block's free state changes: mark_free(), mark_allocated(), mark_split(), and the sites in __gpu_buddy_free(), __force_merge(), and the four err_undo paths that call rbtree_remove() directly on free blocks without going through mark_*(). The print functions are simplified as a result: the rbtree traversal is replaced by a direct array lookup. v3: Update after introducing __gpu_buddy_undo_splits() helper v2: Update after fix for use-after-free in split_block() call sites Assisted-by: GitHub Copilot:claude-sonnet-4.6 Reviewed-by: Matthew Auld Link: https://lore.kernel.org/r/20260522092600.32818-5-francois.dugast@intel.com Signed-off-by: Francois Dugast

drm/buddy: Integrate lockdep annotations for gpu buddy manager

2026-05-08T13:46:19+00:00

gpu_buddy APIs are expected to be called with the driver-provided lock held, but there is no runtime enforcement of this contract. Add lockdep annotations to catch locking violations early. Introduce gpu_buddy_driver_set_lock() for the driver to register the lock that protects the buddy manager. Add gpu_buddy_driver_lock_held() assertions to all exported gpu_buddy and drm_buddy APIs that access/modify the manager state. The lock_dep_map field is only compiled in when CONFIG_LOCKDEP is enabled, adding zero overhead to production builds. Wire up xe_ttm_vram_mgr to register its mutex with the buddy manager after initialization. Assisted-by: Copilot:claude-opus-4.6 Suggested-by: Matthew Brost Signed-off-by: Tejas Upadhyay Reviewed-by: Matthew Auld Signed-off-by: Arunpravin Paneer Selvam Link: https://patch.msgid.link/20260508065544.4049240-2-tejas.upadhyay@intel.com

drm/buddy: Improve offset-aligned allocation handling

2026-03-09T07:06:10+00:00

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

drm/buddy: Move internal helpers to buddy.c

2026-02-23T06:51:05+00:00

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

drm/buddy: Add kernel-doc for allocator structures and flags

2026-02-23T06:50:34+00:00

Add missing kernel-doc for GPU buddy allocator flags, gpu_buddy_block, and gpu_buddy. The documentation covers block header fields, allocator roots, free trees, and allocation flags such as RANGE, TOPDOWN, CONTIGUOUS, CLEAR, and TRIM_DISABLE. Private members are marked with kernel-doc private markers and documented with regular comments. No functional changes. v2: - Corrected GPU_BUDDY_CLEAR_TREE and GPU_BUDDY_DIRTY_TREE index values (Arun) - Rebased after DRM buddy allocator moved to drivers/gpu/ - Updated commit message v3: - Document reserved bits 8:6 in header layout (Arun) - Fix checkpatch warning 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/20260212092527.718455-5-sanjay.kumar.yadav@intel.com

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

2026-02-06T01:38:35+00:00

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)

2026-02-06T01:34:02+00:00