On 23-10-2026 11:09, Yadav, Sanjay Kumar wrote:

On 22-10-2026 15:15, Matthew Auld wrote:
On 22/10/2026 06:15, Sanjay Yadav wrote:
gpu_test_buddy_range_bias_pruning fills a 128 MiB range of a 512 MiB
manager with 4K range allocations. It checks top-down placement, that
the exhausted range advertises GPU_BUDDY_NO_FREE_ORDER, -ENOSPC inside
the range while space outside stays usable, and that freed holes are
found again. To check pruning itself, it hides the only free block
behind an ancestor that advertises no free space and expects -ENOSPC;
without pruning the search would return that block. Allocation time is
reported but not asserted.

gpu_test_buddy_free_order_tracking covers root creation, split,
allocation, partial and full coalescing (4K vs 64K), rollback of a
partially satisfied request, gpu_buddy_block_trim() with and without an
explicit start, exact-range, clear and top-down allocations, and
teardown.

Both use a helper that checks every block's subtree_max_free_order
against its state and its children.

v3: (Sashiko)
- Use div_u64() to avoid an __aeabi_uldivmod failure on 32-bit
   architectures.

Cc: Matthew Auld <[email protected]>
Cc: Arun Pravin <[email protected]>
Cc: Joel Fernandes <[email protected]>
Assisted-by: LLM
Signed-off-by: Sanjay Yadav <[email protected]>
---
  drivers/gpu/tests/gpu_buddy_test.c | 308 +++++++++++++++++++++++++++++
  1 file changed, 308 insertions(+)

+308, do we need all of this? IIUC we are optimising the range_bias to short-circuit earlier, by now tracking the largest free order for a subtree. Is it not enough to rely on the existing range_bias tests for correctness? Could those not be extended, if we are missing something in terms of coverage?
existing range_bias test already covers every case where the
patch could hand out the wrong block or fail spuriously. The extra
tests were mostly checking the bookkeeping itself.

Also, ideally we don't want the kunit reaching too much into the gory internals here, except maybe in special cases. For the most part it should just use the exposed API.
Makes sense. For v4 I will replace them with a single
KUNIT_CASE_SLOW perf test in the style of the existing
fragmentation/dirty_tracker ones, using only the public API

 - fill a 128M window at the bottom of a 512M mm with 4K
    GPU_BUDDY_RANGE_ALLOCATION allocs
  - report the time via kunit_info() (not asserted)
  - check top-down placement and -ENOSPC once the window is full
at least shows the quadratic behaviour going away.

If you'd rather not carry a perf test at all?

Thanks,
Sanjay
Gentle ping


diff --git a/drivers/gpu/tests/gpu_buddy_test.c b/drivers/gpu/tests/gpu_buddy_test.c
index 2c6f1da1a6d1..76392329e9e2 100644
--- a/drivers/gpu/tests/gpu_buddy_test.c
+++ b/drivers/gpu/tests/gpu_buddy_test.c
@@ -1595,6 +1595,312 @@ static void gpu_test_buddy_addr_to_block(struct kunit *test)
      gpu_buddy_fini(&mm);
  }
  +static bool gpu_test_block_is_split(struct gpu_buddy_block *block)
+{
+    return (block->header & GPU_BUDDY_HEADER_STATE) == GPU_BUDDY_SPLIT;
+}
+
+static void gpu_test_check_free_order(struct kunit *test, struct gpu_buddy *mm)
+{
+    struct gpu_buddy_block *block, *bad = NULL;
+    unsigned int nr_bad = 0;
+    s8 expected, bad_expected = 0;
+    LIST_HEAD(dfs);
+    unsigned int i;
+
+    for (i = 0; i < mm->n_roots; i++)
+        list_add_tail(&mm->roots[i]->tmp_link, &dfs);
+
+    while ((block = list_first_entry_or_null(&dfs, struct gpu_buddy_block,
+                         tmp_link))) {
+        list_del(&block->tmp_link);
+
+        if (gpu_buddy_block_is_free(block)) {
+            expected = gpu_buddy_block_order(block);
+        } else if (gpu_test_block_is_split(block)) {
+            expected = max(block->left->subtree_max_free_order,
+ block->right->subtree_max_free_order);
+            list_add(&block->right->tmp_link, &dfs);
+            list_add(&block->left->tmp_link, &dfs);
+        } else {
+            expected = GPU_BUDDY_NO_FREE_ORDER;
+        }
+
+        if (block->subtree_max_free_order != expected && !nr_bad++) {
+            bad = block;
+            bad_expected = expected;
+        }
+    }
+
+    KUNIT_EXPECT_EQ_MSG(test, nr_bad, 0U,
+                "first stale block: offset=%#llx order=%u stored=%d expected=%d",
+                bad ? gpu_buddy_block_offset(bad) : 0,
+                bad ? gpu_buddy_block_order(bad) : 0,
+                bad ? bad->subtree_max_free_order : 0, bad_expected);
+}
+
+static struct gpu_buddy_block *
+gpu_test_find_block(struct gpu_buddy *mm, u64 offset, unsigned int order)
+{
+    struct gpu_buddy_block *block;
+    unsigned int i;
+
+    for (i = 0; i < mm->n_roots; i++) {
+        u64 start;
+
+        block = mm->roots[i];
+        start = gpu_buddy_block_offset(block);
+        if (offset < start || offset >= start + gpu_buddy_block_size(mm, block))
+            continue;
+
+        while (gpu_buddy_block_order(block) > order) {
+            if (!gpu_test_block_is_split(block))
+                return NULL;
+            block = offset < gpu_buddy_block_offset(block->right) ?
+                block->left : block->right;
+        }
+        return block;
+    }
+
+    return NULL;
+}
+
+static struct gpu_buddy_block *
+gpu_test_take_block(struct list_head *blocks, u64 offset)
+{
+    struct gpu_buddy_block *block;
+
+    list_for_each_entry(block, blocks, link) {
+        if (gpu_buddy_block_offset(block) == offset) {
+            list_del(&block->link);
+            return block;
+        }
+    }
+
+    return NULL;
+}
+
+static void gpu_test_buddy_range_bias_pruning(struct kunit *test)
+{
+    const u64 mm_size = SZ_512M, range_end = SZ_128M, chunk = SZ_4K;
+    const unsigned int nr = range_end / chunk, window = 1024;
+    const u64 holes[] = { 0, range_end / 2 + 3 * chunk };
+    struct gpu_buddy_block *block, *hidden;
+    u64 first_ns = 0, last_ns = 0;
+    unsigned int i, misplaced = 0;
+    LIST_HEAD(allocated);
+    struct gpu_buddy mm;
+    LIST_HEAD(tmp);
+    int err;
+
+    KUNIT_ASSERT_FALSE_MSG(test, gpu_buddy_init(&mm, mm_size, chunk),
+                   "buddy_init failed\n");
+    KUNIT_ASSERT_EQ(test, mm.n_roots, 1U);
+
+    /*
+     * Small-BAR pattern: order-0 allocations confined to a low prefix of a +     * larger manager. Top-down placement packs them right below range_end, +     * so without pruning every allocation walks all previously allocated
+     * blocks and the total cost is quadratic.
+     */
+    for (i = 0; i < nr; i++) {
+        ktime_t start = ktime_get();
+        u64 elapsed;
+
+        err = gpu_buddy_alloc_blocks(&mm, 0, range_end, chunk, chunk,
+                         &allocated, GPU_BUDDY_RANGE_ALLOCATION);
+        elapsed = ktime_to_ns(ktime_sub(ktime_get(), start));
+        KUNIT_ASSERT_EQ_MSG(test, err, 0, "range alloc %u failed\n", i);
+
+        if (i < window)
+            first_ns += elapsed;
+        else if (i >= nr - window)
+            last_ns += elapsed;
+
+        block = list_last_entry(&allocated, struct gpu_buddy_block, link); +        if (gpu_buddy_block_offset(block) != range_end - (u64)(i + 1) * chunk)
+            misplaced++;
+    }
+
+    kunit_info(test, "first %u range allocs: %llu us, last %u: %llu us\n",
+           window, div_u64(first_ns, NSEC_PER_USEC),
+           window, div_u64(last_ns, NSEC_PER_USEC));
+
+    /* Top-down placement inside the range is unchanged */
+    KUNIT_EXPECT_EQ(test, misplaced, 0U);
+
+    /* The exhausted range advertises no free space, so it is pruned */
+    block = gpu_test_find_block(&mm, 0, ilog2(range_end / chunk));
+    KUNIT_ASSERT_NOT_NULL(test, block);
+    KUNIT_EXPECT_EQ(test, block->subtree_max_free_order, GPU_BUDDY_NO_FREE_ORDER);
+    gpu_test_check_free_order(test, &mm);
+
+    KUNIT_EXPECT_EQ(test, gpu_buddy_alloc_blocks(&mm, 0, range_end, chunk, chunk,
+                             &tmp, GPU_BUDDY_RANGE_ALLOCATION),
+            -ENOSPC);
+
+    KUNIT_ASSERT_FALSE(test, gpu_buddy_alloc_blocks(&mm, 0, mm_size, chunk, chunk,
+                            &tmp, 0));
+    block = list_first_entry(&tmp, struct gpu_buddy_block, link);
+    KUNIT_EXPECT_GE(test, gpu_buddy_block_offset(block), range_end);
+    gpu_buddy_free_list(&mm, &tmp, 0);
+
+    /* A single hole, including the very last one in walk order, is found */
+    for (i = 0; i < ARRAY_SIZE(holes); i++) {
+        block = gpu_test_take_block(&allocated, holes[i]);
+        KUNIT_ASSERT_NOT_NULL(test, block);
+        gpu_buddy_free_block(&mm, block);
+        gpu_test_check_free_order(test, &mm);
+
+        KUNIT_ASSERT_FALSE(test, gpu_buddy_alloc_blocks(&mm, 0, range_end,
+                                chunk, chunk, &allocated,
+                                GPU_BUDDY_RANGE_ALLOCATION));
+        block = list_last_entry(&allocated, struct gpu_buddy_block, link); +        KUNIT_EXPECT_EQ(test, gpu_buddy_block_offset(block), holes[i]);
+    }
+
+    /*
+     * Deterministic pruning check: hide the only free block in the range +     * behind an ancestor that advertises no free space. Without pruning the
+     * search would walk into that subtree and return the block.
+     */
+    block = gpu_test_take_block(&allocated, holes[1]);
+    KUNIT_ASSERT_NOT_NULL(test, block);
+    gpu_buddy_free_block(&mm, block);
+    hidden = gpu_test_find_block(&mm, holes[1], 4);
+    KUNIT_ASSERT_NOT_NULL(test, hidden);
+    KUNIT_ASSERT_EQ(test, hidden->subtree_max_free_order, (s8)0);
+
+    hidden->subtree_max_free_order = GPU_BUDDY_NO_FREE_ORDER;
+    err = gpu_buddy_alloc_blocks(&mm, 0, range_end, chunk, chunk, &tmp,
+                     GPU_BUDDY_RANGE_ALLOCATION);
+    hidden->subtree_max_free_order = 0;
+    KUNIT_EXPECT_EQ(test, err, -ENOSPC);
+    gpu_buddy_free_list(&mm, &tmp, 0);
+    gpu_test_check_free_order(test, &mm);
+
+    gpu_buddy_free_list(&mm, &allocated, 0);
+    gpu_test_check_free_order(test, &mm);
+    KUNIT_EXPECT_EQ(test, mm.roots[0]->subtree_max_free_order, (s8)mm.max_order);
+
+    gpu_buddy_fini(&mm);
+}
+
+static void gpu_test_buddy_free_order_tracking(struct kunit *test)
+{
+    const u64 chunk = SZ_4K;
+    struct gpu_buddy_block *block;
+    LIST_HEAD(allocated);
+    struct gpu_buddy mm;
+    u64 start, avail;
+    LIST_HEAD(big);
+    unsigned int i;
+
+    KUNIT_ASSERT_FALSE(test, gpu_buddy_init(&mm, SZ_8M + SZ_2M + SZ_64K, chunk));
+    KUNIT_EXPECT_EQ(test, mm.n_roots, 3U);
+    for (i = 0; i < mm.n_roots; i++)
+        KUNIT_EXPECT_EQ(test, mm.roots[i]->subtree_max_free_order,
+                (s8)gpu_buddy_block_order(mm.roots[i]));
+    gpu_test_check_free_order(test, &mm);
+    gpu_buddy_fini(&mm);
+
+    KUNIT_ASSERT_FALSE(test, gpu_buddy_init(&mm, SZ_16M, chunk));
+    KUNIT_ASSERT_EQ(test, mm.n_roots, 1U);
+    for (i = 0; i < SZ_4M / chunk; i++)
+        KUNIT_ASSERT_FALSE(test, gpu_buddy_alloc_blocks(&mm, 0, SZ_4M, chunk, chunk,
+                                &allocated,
+                                GPU_BUDDY_RANGE_ALLOCATION));
+    gpu_test_check_free_order(test, &mm);
+
+    /* Partial coalescing up to order 3 must not satisfy a 64K request */
+    for (i = 0; i < SZ_64K / chunk - 1; i++) {
+        block = gpu_test_take_block(&allocated, SZ_1M + i * chunk);
+        KUNIT_ASSERT_NOT_NULL(test, block);
+        gpu_buddy_free_block(&mm, block);
+    }
+    gpu_test_check_free_order(test, &mm);
+
+    /* A partially satisfied request is rolled back on -ENOSPC */
+    avail = mm.avail;
+    KUNIT_EXPECT_EQ(test, gpu_buddy_alloc_blocks(&mm, 0, SZ_4M, SZ_128K, chunk, &big,
+                             GPU_BUDDY_RANGE_ALLOCATION),
+            -ENOSPC);
+    KUNIT_EXPECT_EQ(test, mm.avail, avail);
+    KUNIT_EXPECT_TRUE(test, list_empty(&big));
+    gpu_test_check_free_order(test, &mm);
+
+    KUNIT_EXPECT_EQ(test, gpu_buddy_alloc_blocks(&mm, 0, SZ_4M, SZ_64K, SZ_64K, &big,
+                             GPU_BUDDY_RANGE_ALLOCATION),
+            -ENOSPC);
+    gpu_test_check_free_order(test, &mm);
+
+    /* SPLIT -> FREE: the last buddy coalesces the window into a 64K block */
+    block = gpu_test_take_block(&allocated, SZ_1M + SZ_64K - chunk);
+    KUNIT_ASSERT_NOT_NULL(test, block);
+    gpu_buddy_free_block(&mm, block);
+    gpu_test_check_free_order(test, &mm);
+    KUNIT_ASSERT_FALSE(test, gpu_buddy_alloc_blocks(&mm, 0, SZ_4M, SZ_64K, SZ_64K, &big,
+                            GPU_BUDDY_RANGE_ALLOCATION));
+    block = list_last_entry(&big, struct gpu_buddy_block, link);
+    KUNIT_EXPECT_EQ(test, gpu_buddy_block_offset(block), (u64)SZ_1M);
+    KUNIT_EXPECT_EQ(test, gpu_buddy_block_size(&mm, block), (u64)SZ_64K);
+    gpu_test_check_free_order(test, &mm);
+
+    /* Trim with an explicit start re-allocates inside the detached block */
+    start = SZ_1M + SZ_16K;
+    KUNIT_ASSERT_FALSE(test, gpu_buddy_block_trim(&mm, &start, SZ_16K, &big));
+    KUNIT_ASSERT_TRUE(test, list_is_singular(&big));
+    block = list_first_entry(&big, struct gpu_buddy_block, link);
+    KUNIT_EXPECT_EQ(test, gpu_buddy_block_offset(block), start);
+    KUNIT_EXPECT_EQ(test, gpu_buddy_block_size(&mm, block), (u64)SZ_16K);
+    gpu_test_check_free_order(test, &mm);
+
+    /* Exact-range allocation */
+    KUNIT_ASSERT_FALSE(test, gpu_buddy_alloc_blocks(&mm, SZ_8M, SZ_8M + SZ_256K,
+                            SZ_256K, chunk, &big, 0));
+    gpu_test_check_free_order(test, &mm);
+
+    /* Cleared frees, clear range allocation and top-down allocation */
+    gpu_buddy_free_list(&mm, &big, GPU_BUDDY_CLEARED);
+    gpu_test_check_free_order(test, &mm);
+    KUNIT_ASSERT_FALSE(test, gpu_buddy_alloc_blocks(&mm, SZ_4M, SZ_16M, SZ_128K, chunk,
+                            &big,
+                            GPU_BUDDY_RANGE_ALLOCATION |
+                            GPU_BUDDY_CLEAR_ALLOCATION));
+    gpu_test_check_free_order(test, &mm);
+    KUNIT_ASSERT_FALSE(test, gpu_buddy_alloc_blocks(&mm, 0, SZ_16M, SZ_1M, chunk, &big,
+                            GPU_BUDDY_TOPDOWN_ALLOCATION));
+    gpu_test_check_free_order(test, &mm);
+
+    gpu_buddy_free_list(&mm, &big, 0);
+    gpu_buddy_free_list(&mm, &allocated, 0);
+    gpu_test_check_free_order(test, &mm);
+    KUNIT_EXPECT_EQ(test, mm.roots[0]->subtree_max_free_order, (s8)mm.max_order);
+    gpu_buddy_fini(&mm);
+
+    /*
+     * Contiguous non-power-of-two allocations are trimmed, which re-allocates +     * inside a temporarily detached block. Ancestors must still be updated.
+     */
+    KUNIT_ASSERT_FALSE(test, gpu_buddy_init(&mm, SZ_32K, chunk));
+    KUNIT_ASSERT_EQ(test, mm.n_roots, 1U);
+    for (i = 0; i < 2; i++) {
+        KUNIT_ASSERT_FALSE(test, gpu_buddy_alloc_blocks(&mm, 0, SZ_32K,
+                                SZ_8K + SZ_4K, chunk,
+                                &allocated,
+ GPU_BUDDY_CONTIGUOUS_ALLOCATION));
+        gpu_test_check_free_order(test, &mm);
+    }
+    KUNIT_EXPECT_EQ(test, mm.roots[0]->subtree_max_free_order, (s8)0);
+    KUNIT_EXPECT_EQ(test, gpu_buddy_alloc_blocks(&mm, 0, SZ_32K, SZ_8K, SZ_8K, &big,
+                             GPU_BUDDY_RANGE_ALLOCATION),
+            -ENOSPC);
+
+    gpu_buddy_free_list(&mm, &allocated, 0);
+    gpu_test_check_free_order(test, &mm);
+    gpu_buddy_fini(&mm);
+}
+
  static int gpu_buddy_suite_init(struct kunit_suite *suite)
  {
      while (!random_seed)
@@ -1621,6 +1927,8 @@ static struct kunit_case gpu_buddy_tests[] = {
      KUNIT_CASE(gpu_test_buddy_offset_aligned_allocation),
KUNIT_CASE(gpu_test_buddy_subtree_offset_alignment_stress),
      KUNIT_CASE(gpu_test_buddy_addr_to_block),
+    KUNIT_CASE(gpu_test_buddy_range_bias_pruning),
+    KUNIT_CASE(gpu_test_buddy_free_order_tracking),
      {}
  };

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