What do you mean the first in the chain ? and also can you explain the " perfect match." ? thanks
Assume there is couple nodes equal to the size you requested, without this patch it will traveler to the bottom level of the RB tree and gives you
the node that close to the bottom level, which takes more time compared with break on the first node, but anyway you eventually get the node with the same size
if there is no node that equal to the size you requested, without or with my patch the logic is totally the same.
/Monk
-----Original Message-----
From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Sent: Friday, November 23, 2018 5:03 PM
To: Liu, Monk <Monk.Liu@xxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: FW: [PATCH] drm: should break if already get the best size
Quoting Liu, Monk (2018-11-23 08:02:11)
>
>
> -----Original Message-----
> From: amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of
> Monk Liu
> Sent: Thursday, November 22, 2018 8:33 PM
> To: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: Liu, Monk <Monk.Liu@xxxxxxx>
> Subject: [PATCH] drm: should break if already get the best size
>
> Signed-off-by: Monk Liu <Monk.Liu@xxxxxxx>
> ---
> 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;
No. The point is to find the first in the chain that matches because not every node is suitable. By not checking all best_sizes you may end up skipping the perfect match.
-Chris
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