On Fri, May 08, 2026 at 03:13:04PM +0100, Matthew Auld wrote:
> On 04/05/2026 14:52, 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().
> >
> > Signed-off-by: Francois Dugast <[email protected]>
> > Assisted-by: GitHub Copilot:claude-sonnet-4.6
>
> Reviewed-by: Matthew Auld <[email protected]>
>
> Note that Sashiko found an existing issue here:
> https://sashiko.dev/#/patchset/20260504135343.1797869-1-francois.dugast%40intel.com
>
> I guess would be good to fix that first, in this series?
Yes indeed! Please see v2.
Francois
>
> > ---
> > drivers/gpu/buddy.c | 29 +++++++++++++++++++++++------
> > drivers/gpu/drm/drm_buddy.c | 8 +++++---
> > include/linux/gpu_buddy.h | 8 ++++++++
> > 3 files changed, 36 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/gpu/buddy.c b/drivers/gpu/buddy.c
> > index d831165e87ea..ebef03613b3f 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);
> > @@ -398,6 +405,12 @@ 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);
> > @@ -462,6 +475,8 @@ int gpu_buddy_init(struct gpu_buddy *mm, u64 size, u64
> > chunk_size)
> > kfree(mm->free_trees[i]);
> > kfree(mm->free_trees);
> > out_free_scoreboard:
> > + kfree(mm->used_scoreboard);
> > +out_free_free_scoreboard:
> > kfree(mm->free_scoreboard);
> > return -ENOMEM;
> > }
> > @@ -502,6 +517,7 @@ 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);
> > @@ -1496,15 +1512,16 @@ 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);
> > + u64 free_count = mm->free_scoreboard[order];
> > + u64 used_count = mm->used_scoreboard[order];
> > + u64 free = free_count * (mm->chunk_size << order);
> > if (free < SZ_1M)
> > - pr_info("order-%2d free: %8llu KiB, blocks: %llu\n",
> > - order, free >> 10, count);
> > + pr_info("order-%2d free: %8llu KiB, free_blocks: %llu,
> > used_blocks: %llu\n",
> > + order, free >> 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, free_blocks: %llu,
> > used_blocks: %llu\n",
> > + order, free >> 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 7839b54d3da7..3a1cb06923c6 100644
> > --- a/drivers/gpu/drm/drm_buddy.c
> > +++ b/drivers/gpu/drm/drm_buddy.c
> > @@ -46,8 +46,9 @@ 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 free = free_count * (mm->chunk_size << order);
> > drm_printf(p, "order-%2d ", order);
> > @@ -56,7 +57,8 @@ void drm_buddy_print(struct gpu_buddy *mm, struct
> > drm_printer *p)
> > else
> > drm_printf(p, "free: %8llu MiB", free >> 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 250841ca4bcf..b1cad7833dc1 100644
> > --- a/include/linux/gpu_buddy.h
> > +++ b/include/linux/gpu_buddy.h
> > @@ -179,6 +179,14 @@ struct gpu_buddy {
> > * mark_split() when a block leaves the free state.
> > */
> > 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
> > + * gpu_buddy_free_block() which is the sole entry point for freeing
> > + * allocated blocks.
> > + */
> > + u64 *used_scoreboard;
> > /* public: */
> > unsigned int n_roots;
> > unsigned int max_order;
>
