[PATCH 3/8] drm: implement top-down allocation method
Matthew Auld
matthew.auld at intel.com
Wed Nov 3 18:44:34 UTC 2021
On 25/10/2021 14:00, Arunpravin wrote:
> Implemented a function which walk through the order list,
> compares the offset and returns the maximum offset block,
> this method is unpredictable in obtaining the high range
> address blocks which depends on allocation and deallocation.
> for instance, if driver requests address at a low specific
> range, allocator traverses from the root block and splits
> the larger blocks until it reaches the specific block and
> in the process of splitting, lower orders in the freelist
> are occupied with low range address blocks and for the
> subsequent TOPDOWN memory request we may return the low
> range blocks.To overcome this issue, we may go with the
> below approach.
>
> The other approach, sorting each order list entries in
> ascending order and compares the last entry of each
> order list in the freelist and return the max block.
> This creates sorting overhead on every drm_buddy_free()
> request and split up of larger blocks for a single page
> request.
>
> Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam at amd.com>
> ---
> drivers/gpu/drm/drm_buddy.c | 42 +++++++++++++++++++++++++++++++------
> include/drm/drm_buddy.h | 1 +
> 2 files changed, 37 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
> index 406e3d521903..9d3547bcc5da 100644
> --- a/drivers/gpu/drm/drm_buddy.c
> +++ b/drivers/gpu/drm/drm_buddy.c
> @@ -362,6 +362,27 @@ alloc_range(struct drm_buddy_mm *mm,
> return ERR_PTR(err);
> }
>
> +static struct drm_buddy_block *
> +get_maxblock(struct list_head *head)
> +{
> + struct drm_buddy_block *max_block = NULL, *node;
> +
> + max_block = list_first_entry_or_null(head,
> + struct drm_buddy_block,
> + link);
> +
> + if (!max_block)
> + return NULL;
> +
> + list_for_each_entry(node, head, link) {
> + if (drm_buddy_block_offset(node) >
> + drm_buddy_block_offset(max_block))
Alignment.
> + max_block = node;
> + }
I suppose there will be pathological cases where this will unnecessarily
steal the mappable portion? But in practice maybe this is good enough?
> +
> + return max_block;
> +}
> +
> static struct drm_buddy_block *
> alloc_from_freelist(struct drm_buddy_mm *mm,
> unsigned int order,
> @@ -372,13 +393,22 @@ alloc_from_freelist(struct drm_buddy_mm *mm,
> int err;
>
> for (i = order; i <= mm->max_order; ++i) {
> - if (!list_empty(&mm->free_list[i])) {
> - block = list_first_entry_or_null(&mm->free_list[i],
> - struct drm_buddy_block,
> - link);
> + if (flags & DRM_BUDDY_TOPDOWN_ALLOCATION) {
> + if (!list_empty(&mm->free_list[i])) {
AFAIK no need to keep checking list_empty(), below also.
> + block = get_maxblock(&mm->free_list[i]);
>
> - if (block)
> - break;
> + if (block)
> + break;
> + }
> + } else {
> + if (!list_empty(&mm->free_list[i])) {
> + block = list_first_entry_or_null(&mm->free_list[i],
> + struct drm_buddy_block,
> + link);
> +
> + if (block)
> + break;
> + }
> }
> }
>
> diff --git a/include/drm/drm_buddy.h b/include/drm/drm_buddy.h
> index c7bb5509a7ad..cd8021d2d6e7 100644
> --- a/include/drm/drm_buddy.h
> +++ b/include/drm/drm_buddy.h
> @@ -28,6 +28,7 @@
> })
>
> #define DRM_BUDDY_RANGE_ALLOCATION (1 << 0)
> +#define DRM_BUDDY_TOPDOWN_ALLOCATION (1 << 1)
>
> struct drm_buddy_block {
> #define DRM_BUDDY_HEADER_OFFSET GENMASK_ULL(63, 12)
>
More information about the dri-devel
mailing list