[PATCH v2] drm: Optimise for continuous memory allocation

[xinhui pan <xinhui.pan@xxxxxxx>]

Currently drm-buddy does not have full knowledge of continuous memory.

Lets consider scenario below.
order 1:    L		    R
order 0: LL	LR	RL	RR
for order 1 allocation, it can offer L or R or LR+RL.

For now, we only implement L or R case for continuous memory allocation.
So this patch aims to implement the LR+RL case.

Signed-off-by: xinhui pan <xinhui.pan@xxxxxxx>
---
change from v1:
implement top-down continuous allocation
---
 drivers/gpu/drm/drm_buddy.c | 66 +++++++++++++++++++++++++++++++++----
 1 file changed, 59 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index 11bb59399471..eea14505070e 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -386,6 +386,46 @@ alloc_range_bias(struct drm_buddy *mm,
 	return ERR_PTR(err);
 }
 
+static struct drm_buddy_block *
+find_continuous_blocks(struct drm_buddy *mm,
+		       int order,
+		       unsigned long flags,
+		       struct drm_buddy_block **rn)
+{
+	struct list_head *head = &mm->free_list[order];
+	struct drm_buddy_block *node, *parent, *free_node, *max_node = NULL;
+
+	list_for_each_entry(free_node, head, link) {
+		if (max_node) {
+			if (!(flags & DRM_BUDDY_TOPDOWN_ALLOCATION))
+				break;
+
+			if (drm_buddy_block_offset(free_node) <
+			    drm_buddy_block_offset(max_node))
+				continue;
+		}
+
+		parent = free_node;
+		do {
+			node = parent;
+			parent = parent->parent;
+		} while (parent && parent->right == node);
+		if (!parent)
+			continue;
+
+		node = parent->right;
+		while (drm_buddy_block_is_split(node))
+			node = node->left;
+
+		if (drm_buddy_block_is_free(node) &&
+		    drm_buddy_block_order(node) == order) {
+			*rn = node;
+			max_node = free_node;
+		}
+	}
+	return max_node;
+}
+
 static struct drm_buddy_block *
 get_maxblock(struct list_head *head)
 {
@@ -637,7 +677,7 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
 			   struct list_head *blocks,
 			   unsigned long flags)
 {
-	struct drm_buddy_block *block = NULL;
+	struct drm_buddy_block *block = NULL, *rblock = NULL;
 	unsigned int min_order, order;
 	unsigned long pages;
 	LIST_HEAD(allocated);
@@ -689,17 +729,29 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
 				break;
 
 			if (order-- == min_order) {
+				if (!(flags & DRM_BUDDY_RANGE_ALLOCATION) &&
+				    min_order != 0 && pages == BIT(order + 1)) {
+					block = find_continuous_blocks(mm,
+								       order,
+								       flags,
+								       &rblock);
+					if (block)
+						break;
+				}
 				err = -ENOSPC;
 				goto err_free;
 			}
 		} while (1);
 
-		mark_allocated(block);
-		mm->avail -= drm_buddy_block_size(mm, block);
-		kmemleak_update_trace(block);
-		list_add_tail(&block->link, &allocated);
-
-		pages -= BIT(order);
+		do {
+			mark_allocated(block);
+			mm->avail -= drm_buddy_block_size(mm, block);
+			kmemleak_update_trace(block);
+			list_add_tail(&block->link, &allocated);
+			pages -= BIT(order);
+			block = rblock;
+			rblock = NULL;
+		} while (block);
 
 		if (!pages)
 			break;
-- 
2.34.1