The buddy allocator previously pre-built a DFS list by inserting all root blocks via list_add_tail() before every allocation call in __alloc_range_bias() and __gpu_buddy_alloc_range(). This is wasteful when the allocation can be satisfied by the first root or by sub-blocks produced from splits, as the remaining roots are never consumed.
Introduce __get_candidate_block() which unifies the block acquisition logic for both __alloc_range_bias() and __alloc_range(): it first checks the DFS list (populated by splits during allocation or pre-filled by the caller for trim), and only when the list is exhausted does it lazily fetch the next root block through a cursor. When the caller pre-fills the DFS list (trim scenario), the cursor is initialized to mm->n_roots to disable root iteration entirely, preserving the original behavior. Signed-off-by: Zhaoyu Liu <[email protected]> Suggested-by: Arun Pravin <[email protected]> --- v2: - Change __get_candidate_block to inline - Link to v1: https://lore.kernel.org/all/ak+ECwsuSljmvyKd@hostpc/ --- drivers/gpu/buddy.c | 61 ++++++++++++++++++++++++++++++--------------- 1 file changed, 41 insertions(+), 20 deletions(-) diff --git a/drivers/gpu/buddy.c b/drivers/gpu/buddy.c index dc81fe0301ce..63b3959973fa 100644 --- a/drivers/gpu/buddy.c +++ b/drivers/gpu/buddy.c @@ -700,6 +700,41 @@ static void __gpu_buddy_undo_splits(struct gpu_buddy *mm, } } +/** + * __get_candidate_block - Get a candidate block for allocation. + * @mm: GPU buddy manager + * @dfs: List of candidate blocks. Populated in two ways: (1) pre-filled by + * the caller before allocation with blocks available for allocation, + * and (2) extended during allocation by block splits, which add the + * resulting sub-blocks for subsequent finer-grained allocation. + * @cursor: Pointer to current root index, advanced when iterating roots. + * Pass in a value >= mm->n_roots to disable root iteration entirely, + * restricting block acquisition to @dfs only; this is used in the + * trim scenario where only pre-split sub-blocks should be considered. + * + * Return: Pointer to the acquired block on success, ERR_PTR(-ENOSPC) when no + * more blocks are available. + */ +static inline struct gpu_buddy_block* +__get_candidate_block(struct gpu_buddy *mm, struct list_head *dfs, + uint32_t *cursor) +{ + struct gpu_buddy_block *block; + + block = list_first_entry_or_null(dfs, + struct gpu_buddy_block, + tmp_link); + if (block) { + list_del(&block->tmp_link); + return block; + } + + if (*cursor >= mm->n_roots) + return ERR_PTR(-ENOSPC); + + return mm->roots[(*cursor)++]; +} + static struct gpu_buddy_block * __alloc_range_bias(struct gpu_buddy *mm, u64 start, u64 end, @@ -711,25 +746,18 @@ __alloc_range_bias(struct gpu_buddy *mm, struct gpu_buddy_block *block; LIST_HEAD(dfs); int err; - int i; + uint32_t cursor = 0; end = end - 1; - for (i = 0; i < mm->n_roots; ++i) - list_add_tail(&mm->roots[i]->tmp_link, &dfs); - do { u64 block_start; u64 block_end; - block = list_first_entry_or_null(&dfs, - struct gpu_buddy_block, - tmp_link); - if (!block) + block = __get_candidate_block(mm, &dfs, &cursor); + if (IS_ERR(block)) break; - list_del(&block->tmp_link); - if (gpu_buddy_block_order(block) < order) continue; @@ -1023,6 +1051,7 @@ static int __alloc_range(struct gpu_buddy *mm, LIST_HEAD(allocated); u64 end; int err; + uint32_t cursor = list_empty(dfs) ? 0 : mm->n_roots; end = start + size - 1; @@ -1030,14 +1059,10 @@ static int __alloc_range(struct gpu_buddy *mm, u64 block_start; u64 block_end; - block = list_first_entry_or_null(dfs, - struct gpu_buddy_block, - tmp_link); - if (!block) + block = __get_candidate_block(mm, dfs, &cursor); + if (IS_ERR(block)) break; - list_del(&block->tmp_link); - block_start = gpu_buddy_block_offset(block); block_end = block_start + gpu_buddy_block_size(mm, block) - 1; @@ -1109,10 +1134,6 @@ static int __gpu_buddy_alloc_range(struct gpu_buddy *mm, struct list_head *blocks) { LIST_HEAD(dfs); - int i; - - for (i = 0; i < mm->n_roots; ++i) - list_add_tail(&mm->roots[i]->tmp_link, &dfs); return __alloc_range(mm, &dfs, start, size, blocks, total_allocated_on_err); -- 2.34.1
