From 5640e81607152d7f2d2558227c0f6cb78b8f39cf Mon Sep 17 00:00:00 2001
From: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Date: Thu, 12 Jan 2023 04:00:27 -0800
Subject: [PATCH] drm: Optimize drm buddy top-down allocation method
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Git-commit: 5640e81607152d7f2d2558227c0f6cb78b8f39cf
Patch-mainline: v6.2-rc4
References: git-fixes

We are observing performance drop in many usecases which include
games, 3D benchmark applications,etc.. To solve this problem, We
are strictly not allowing top down flag enabled allocations to
steal the memory space from cpu visible region.

The idea 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 3D benchmark scores and solves
fragmentation issues.

All drm buddy selftests are verfied.
Drm_buddy: pass:6 fail:0 skip:0 total:6

Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230112120027.3072-1-Arunpravin.PaneerSelvam@amd.com
Signed-off-by: Christian König <christian.koenig@amd.com>
Cc: Cc: stable@vger.kernel.org # 5.18+
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 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..3d1f50f481cf 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);
 }
-- 
2.35.3