On Mon, May 18, 2026 at 05:02:32PM +0100, Matthew Auld wrote: > On 18/05/2026 15:14, Francois Dugast wrote: > > 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(). > > > > 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 > > > > Signed-off-by: Francois Dugast <[email protected]> > > Assisted-by: GitHub Copilot:claude-sonnet-4.6 > > Could potentially also assert that used_scoreboard is empty at fini(), as a > quick sanity check that nothing got leaked/missed with the accounting. Would > also then be checked across the selftests.
Good idea, will do. > > Reviewed-by: Matthew Auld <[email protected]> > > > --- > > drivers/gpu/buddy.c | 39 +++++++++++++++++++++++++++---------- > > drivers/gpu/drm/drm_buddy.c | 18 +++++++++++------ > > include/linux/gpu_buddy.h | 8 ++++++++ > > 3 files changed, 49 insertions(+), 16 deletions(-) > > > > diff --git a/drivers/gpu/buddy.c b/drivers/gpu/buddy.c > > index de18b63fef0a..f81d0d8fde15 100644 > > --- a/drivers/gpu/buddy.c > > +++ b/drivers/gpu/buddy.c > > @@ -194,6 +194,7 @@ static void mark_allocated(struct gpu_buddy *mm, > > block->header |= GPU_BUDDY_ALLOCATED; > > mm->free_scoreboard[gpu_buddy_block_order(block)]--; > > + mm->used_scoreboard[gpu_buddy_block_order(block)]++; > > rbtree_remove(mm, block); > > } > > @@ -203,6 +204,9 @@ static void mark_free(struct gpu_buddy *mm, > > { > > enum gpu_buddy_free_tree tree; > > + if (gpu_buddy_block_is_allocated(block)) > > + mm->used_scoreboard[gpu_buddy_block_order(block)]--; > > + > > block->header &= ~GPU_BUDDY_HEADER_STATE; > > block->header |= GPU_BUDDY_FREE; > > @@ -281,6 +285,9 @@ static unsigned int __gpu_buddy_free(struct gpu_buddy > > *mm, > > if (force_merge && gpu_buddy_block_is_clear(buddy)) > > mm->clear_avail -= gpu_buddy_block_size(mm, buddy); > > + if (gpu_buddy_block_is_allocated(block)) > > + mm->used_scoreboard[gpu_buddy_block_order(block)]--; > > + > > gpu_block_free(mm, block); > > gpu_block_free(mm, buddy); > > @@ -398,11 +405,17 @@ int gpu_buddy_init(struct gpu_buddy *mm, u64 size, > > u64 chunk_size) > > if (!mm->free_scoreboard) > > return -ENOMEM; > > + mm->used_scoreboard = kcalloc(mm->max_order + 1, > > + sizeof(*mm->used_scoreboard), > > + GFP_KERNEL); > > + if (!mm->used_scoreboard) > > + goto out_free_free_scoreboard; > > + > > mm->free_trees = kmalloc_array(GPU_BUDDY_MAX_FREE_TREES, > > sizeof(*mm->free_trees), > > GFP_KERNEL); > > if (!mm->free_trees) > > - goto out_free_scoreboard; > > + goto out_free_used_scoreboard; > > for_each_free_tree(i) { > > mm->free_trees[i] = kmalloc_array(mm->max_order + 1, > > @@ -464,7 +477,9 @@ int gpu_buddy_init(struct gpu_buddy *mm, u64 size, u64 > > chunk_size) > > while (i--) > > kfree(mm->free_trees[i]); > > kfree(mm->free_trees); > > -out_free_scoreboard: > > +out_free_used_scoreboard: > > + kfree(mm->used_scoreboard); > > +out_free_free_scoreboard: > > kfree(mm->free_scoreboard); > > return -ENOMEM; > > } > > @@ -505,6 +520,7 @@ void gpu_buddy_fini(struct gpu_buddy *mm) > > kfree(mm->free_trees); > > kfree(mm->roots); > > kfree(mm->free_scoreboard); > > + kfree(mm->used_scoreboard); > > } > > EXPORT_SYMBOL(gpu_buddy_fini); > > @@ -1505,15 +1521,18 @@ void gpu_buddy_print(struct gpu_buddy *mm) > > mm->chunk_size >> 10, mm->size >> 20, mm->avail >> 20, > > mm->clear_avail >> 20); > > for (order = mm->max_order; order >= 0; order--) { > > - u64 count = mm->free_scoreboard[order]; > > - u64 free = count * (mm->chunk_size << order); > > - > > - if (free < SZ_1M) > > - pr_info("order-%2d free: %8llu KiB, blocks: %llu\n", > > - order, free >> 10, count); > > + u64 free_count = mm->free_scoreboard[order]; > > + u64 used_count = mm->used_scoreboard[order]; > > + u64 block_size = mm->chunk_size << order; > > + u64 free = free_count * block_size; > > + u64 used = used_count * block_size; > > + > > + if (block_size < SZ_1M) > > + pr_info("order-%2d free: %8llu KiB, used: %8llu KiB, > > free_blocks: %llu, used_blocks: %llu\n", > > + order, free >> 10, used >> 10, free_count, > > used_count); > > else > > - pr_info("order-%2d free: %8llu MiB, blocks: %llu\n", > > - order, free >> 20, count); > > + pr_info("order-%2d free: %8llu MiB, used: %8llu MiB, > > free_blocks: %llu, used_blocks: %llu\n", > > + order, free >> 20, used >> 20, free_count, > > used_count); > > } > > } > > EXPORT_SYMBOL(gpu_buddy_print); > > diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c > > index eef995e08a37..1536e59c6fe7 100644 > > --- a/drivers/gpu/drm/drm_buddy.c > > +++ b/drivers/gpu/drm/drm_buddy.c > > @@ -47,17 +47,23 @@ void drm_buddy_print(struct gpu_buddy *mm, struct > > drm_printer *p) > > mm->chunk_size >> 10, mm->size >> 20, mm->avail >> 20, > > mm->clear_avail >> 20); > > for (order = mm->max_order; order >= 0; order--) { > > - u64 count = mm->free_scoreboard[order]; > > - u64 free = count * (mm->chunk_size << order); > > + u64 free_count = mm->free_scoreboard[order]; > > + u64 used_count = mm->used_scoreboard[order]; > > + u64 block_size = mm->chunk_size << order; > > + u64 free = free_count * block_size; > > + u64 used = used_count * block_size; > > drm_printf(p, "order-%2d ", order); > > - if (free < SZ_1M) > > - drm_printf(p, "free: %8llu KiB", free >> 10); > > + if (block_size < SZ_1M) > > + drm_printf(p, "free: %8llu KiB, used: %8llu KiB", > > + free >> 10, used >> 10); > > else > > - drm_printf(p, "free: %8llu MiB", free >> 20); > > + drm_printf(p, "free: %8llu MiB, used: %8llu MiB", > > + free >> 20, used >> 20); > > - drm_printf(p, ", blocks: %llu\n", count); > > + drm_printf(p, ", free_blocks: %llu, used_blocks: %llu\n", > > + free_count, used_count); > > } > > } > > EXPORT_SYMBOL(drm_buddy_print); > > diff --git a/include/linux/gpu_buddy.h b/include/linux/gpu_buddy.h > > index a28f7d7637ca..e037714563d8 100644 > > --- a/include/linux/gpu_buddy.h > > +++ b/include/linux/gpu_buddy.h > > @@ -180,6 +180,14 @@ struct gpu_buddy { > > * called on a free block. > > */ > > u64 *free_scoreboard; > > + /* > > + * Per-order used block scoreboard: used_scoreboard[order] holds the > > + * number of blocks of that order currently in the allocated state. > > + * Incremented in mark_allocated(), decremented in mark_free() (guarded > > + * by gpu_buddy_block_is_allocated()) and in __gpu_buddy_free() when an > > + * allocated block is consumed directly during buddy coalescing. > > + */ > > + u64 *used_scoreboard; > > /* public: */ > > unsigned int n_roots; > > unsigned int max_order; >
