[PATCH] drm: Alloc high address for drm buddy topdown flag

[Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@xxxxxxx>]

As we are observing low numbers in viewperf graphics benchmark, we
are strictly not allowing the top down flag enabled allocations
to steal the memory space from cpu visible region.

The approach is, we are sorting each order list entries in
ascending order and compare the last entry of each order
list in the freelist and return the max block.

This patch improves the viewperf 3D benchmark scores.

Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@xxxxxxx>
---
 drivers/gpu/drm/drm_buddy.c | 81 ++++++++++++++++++++++++-------------
 1 file changed, 54 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index 11bb59399471..50916b2f2fc5 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -38,6 +38,25 @@ static void drm_block_free(struct drm_buddy *mm,
 	kmem_cache_free(slab_blocks, block);
 }
 
+static void list_insert_sorted(struct drm_buddy *mm,
+			       struct drm_buddy_block *block)
+{
+	struct drm_buddy_block *node;
+	struct list_head *head;
+
+	head = &mm->free_list[drm_buddy_block_order(block)];
+	if (list_empty(head)) {
+		list_add(&block->link, head);
+		return;
+	}
+
+	list_for_each_entry(node, head, link)
+		if (drm_buddy_block_offset(block) < drm_buddy_block_offset(node))
+			break;
+
+	__list_add(&block->link, node->link.prev, &node->link);
+}
+
 static void mark_allocated(struct drm_buddy_block *block)
 {
 	block->header &= ~DRM_BUDDY_HEADER_STATE;
@@ -52,8 +71,7 @@ static void mark_free(struct drm_buddy *mm,
 	block->header &= ~DRM_BUDDY_HEADER_STATE;
 	block->header |= DRM_BUDDY_FREE;
 
-	list_add(&block->link,
-		 &mm->free_list[drm_buddy_block_order(block)]);
+	list_insert_sorted(mm, block);
 }
 
 static void mark_split(struct drm_buddy_block *block)
@@ -387,20 +405,26 @@ alloc_range_bias(struct drm_buddy *mm,
 }
 
 static struct drm_buddy_block *
-get_maxblock(struct list_head *head)
+get_maxblock(struct drm_buddy *mm, unsigned int order)
 {
 	struct drm_buddy_block *max_block = NULL, *node;
+	unsigned int i;
 
-	max_block = list_first_entry_or_null(head,
-					     struct drm_buddy_block,
-					     link);
-	if (!max_block)
-		return NULL;
+	for (i = order; i <= mm->max_order; ++i) {
+		if (!list_empty(&mm->free_list[i])) {
+			node = list_last_entry(&mm->free_list[i],
+					       struct drm_buddy_block,
+					       link);
+			if (!max_block) {
+				max_block = node;
+				continue;
+			}
 
-	list_for_each_entry(node, head, link) {
-		if (drm_buddy_block_offset(node) >
-		    drm_buddy_block_offset(max_block))
-			max_block = node;
+			if (drm_buddy_block_offset(node) >
+				drm_buddy_block_offset(max_block)) {
+				max_block = node;
+			}
+		}
 	}
 
 	return max_block;
@@ -412,20 +436,23 @@ alloc_from_freelist(struct drm_buddy *mm,
 		    unsigned long flags)
 {
 	struct drm_buddy_block *block = NULL;
-	unsigned int i;
+	unsigned int tmp;
 	int err;
 
-	for (i = order; i <= mm->max_order; ++i) {
-		if (flags & DRM_BUDDY_TOPDOWN_ALLOCATION) {
-			block = get_maxblock(&mm->free_list[i]);
-			if (block)
-				break;
-		} else {
-			block = list_first_entry_or_null(&mm->free_list[i],
-							 struct drm_buddy_block,
-							 link);
-			if (block)
-				break;
+	if (flags & DRM_BUDDY_TOPDOWN_ALLOCATION) {
+		block = get_maxblock(mm, order);
+		if (block)
+			/* Store the obtained block order */
+			tmp = drm_buddy_block_order(block);
+	} else {
+		for (tmp = order; tmp <= mm->max_order; ++tmp) {
+			if (!list_empty(&mm->free_list[tmp])) {
+				block = list_last_entry(&mm->free_list[tmp],
+							struct drm_buddy_block,
+							link);
+				if (block)
+					break;
+			}
 		}
 	}
 
@@ -434,18 +461,18 @@ alloc_from_freelist(struct drm_buddy *mm,
 
 	BUG_ON(!drm_buddy_block_is_free(block));
 
-	while (i != order) {
+	while (tmp != order) {
 		err = split_block(mm, block);
 		if (unlikely(err))
 			goto err_undo;
 
 		block = block->right;
-		i--;
+		tmp--;
 	}
 	return block;
 
 err_undo:
-	if (i != order)
+	if (tmp != order)
 		__drm_buddy_free(mm, block);
 	return ERR_PTR(err);
 }
-- 
2.25.1