[PATCH] drm: should break if already get the best size

Deucher, Alexander Alexander.Deucher at amd.com
Fri Nov 23 19:34:21 UTC 2018

Please add a proper patch description.


From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of Zhu, Rex <Rex.Zhu at amd.com>
Sent: Friday, November 23, 2018 4:44:31 AM
To: Liu, Monk; amd-gfx at lists.freedesktop.org
Subject: Re: [PATCH] drm: should break if already get the best size

Tested-by: Rex Zhu <Rex.Zhu at amd.com>

Without this patch, if we search node via rb tree.

For example: we insert 9999 different node with rand size, size range in (1-9999).

the key in root node is 5587.

if we try to find the node with key equal to 5587 or 7381,

node->key is 5587
node->key is 2273
node->key is 3706
node->key is 4892
node->key is 5296
node->key is 5461
node->key is 5519
node->key is 5549
node->key is 5570
node->key is 5581
node->key is 5584
node->key is 5585
node->key is 5586
node->key is 5586

Find the best node, key is 5587 (Loop 14 levels)

node->key is 5587
node->key is 7381
node->key is 6474
node->key is 7034
node->key is 7228
node->key is 7314
node->key is 7339
node->key is 7349
node->key is 7372
node->key is 7377
node->key is 7378
node->key is 7379
node->key is 7379

find the best node, key is 7381. (Loop 13 levels)

With this patch:

we don't need to go down if we found the right node that size equal to we needed.

Best Regards

From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of Monk Liu <Monk.Liu at amd.com>
Sent: Thursday, November 22, 2018 8:33 PM
To: amd-gfx at lists.freedesktop.org
Cc: Liu, Monk
Subject: [PATCH] drm: should break if already get the best size

Signed-off-by: Monk Liu <Monk.Liu at amd.com>
 drivers/gpu/drm/drm_mm.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
index 3cc5fbd..369fd9b 100644
--- a/drivers/gpu/drm/drm_mm.c
+++ b/drivers/gpu/drm/drm_mm.c
@@ -318,6 +318,8 @@ static struct drm_mm_node *best_hole(struct drm_mm *mm, u64 size)
                 if (size <= node->hole_size) {
                         best = node;
                         rb = rb->rb_right;
+                       if (size == node->hole_size)
+                               break;
                 } else {
                         rb = rb->rb_left;

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