[Intel-gfx] [PATCH v9 4/6] drm: implement a method to free unused pages
Matthew Auld
matthew.auld at intel.com
Thu Jan 20 17:35:26 UTC 2022
On 19/01/2022 11:37, Arunpravin wrote:
> On contiguous allocation, we round up the size
> to the *next* power of 2, implement a function
> to free the unused pages after the newly allocate block.
>
> v2(Matthew Auld):
> - replace function name 'drm_buddy_free_unused_pages' with
> drm_buddy_block_trim
> - replace input argument name 'actual_size' with 'new_size'
> - add more validation checks for input arguments
> - add overlaps check to avoid needless searching and splitting
> - merged the below patch to see the feature in action
> - add free unused pages support to i915 driver
> - lock drm_buddy_block_trim() function as it calls mark_free/mark_split
> are all globally visible
>
> v3(Matthew Auld):
> - remove trim method error handling as we address the failure case
> at drm_buddy_block_trim() function
>
> v4:
> - in case of trim, at __alloc_range() split_block failure path
> marks the block as free and removes it from the original list,
> potentially also freeing it, to overcome this problem, we turn
> the drm_buddy_block_trim() input node into a temporary node to
> prevent recursively freeing itself, but still retain the
> un-splitting/freeing of the other nodes(Matthew Auld)
>
> - modify the drm_buddy_block_trim() function return type
>
> v5(Matthew Auld):
> - revert drm_buddy_block_trim() function return type changes in v4
> - modify drm_buddy_block_trim() passing argument n_pages to original_size
> as n_pages has already been rounded up to the next power-of-two and
> passing n_pages results noop
>
> v6:
> - fix warnings reported by kernel test robot <lkp at intel.com>
>
> Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam at amd.com>
> ---
> drivers/gpu/drm/drm_buddy.c | 65 +++++++++++++++++++
> drivers/gpu/drm/i915/i915_ttm_buddy_manager.c | 10 +++
> include/drm/drm_buddy.h | 4 ++
> 3 files changed, 79 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
> index 6aa5c1ce25bf..c5902a81b8c5 100644
> --- a/drivers/gpu/drm/drm_buddy.c
> +++ b/drivers/gpu/drm/drm_buddy.c
> @@ -546,6 +546,71 @@ static int __drm_buddy_alloc_range(struct drm_buddy *mm,
> return __alloc_range(mm, &dfs, start, size, blocks);
> }
>
> +/**
> + * drm_buddy_block_trim - free unused pages
> + *
> + * @mm: DRM buddy manager
> + * @new_size: original size requested
> + * @blocks: output list head to add allocated blocks
@blocks: Input and output list of allocated blocks. MUST contain single
block as input to be trimmed. On success will contain the newly
allocated blocks making up the @new_size. Blocks always appear in
ascending order.
?
> + *
> + * For contiguous allocation, we round up the size to the nearest
> + * power of two value, drivers consume *actual* size, so remaining
> + * portions are unused and it can be freed.
so remaining portions are unused and can be optionally freed with this
function.
?
> + *
> + * Returns:
> + * 0 on success, error code on failure.
> + */
> +int drm_buddy_block_trim(struct drm_buddy *mm,
> + u64 new_size,
> + struct list_head *blocks)
> +{
> + struct drm_buddy_block *parent;
> + struct drm_buddy_block *block;
> + LIST_HEAD(dfs);
> + u64 new_start;
> + int err;
> +
> + if (!list_is_singular(blocks))
> + return -EINVAL;
> +
> + block = list_first_entry(blocks,
> + struct drm_buddy_block,
> + link);
> +
> + if (!drm_buddy_block_is_allocated(block))
Maybe:
if (WARN_ON(!drm_buddy_block_is_allocated()))
AFAIK it should be normally impossible to be handed such non-allocated
block, and so should be treated as a serious programmer error.
?
> + return -EINVAL;
> +
> + if (new_size > drm_buddy_block_size(mm, block))
> + return -EINVAL;
> +
> + if (!new_size && !IS_ALIGNED(new_size, mm->chunk_size))
> + return -EINVAL;
I assume that's a typo:
if (!new_size || ...)
Otherwise I think looks good. Some unit tests for this would be nice,
but not a blocker. And this does at least pass the igt_mock_contiguous
selftest, and I didn't see anything nasty when running on DG1, which
does make use of TTM_PL_FLAG_CONTIGUOUS,
Reviewed-by: Matthew Auld <matthew.auld at intel.com>
> +
> + if (new_size == drm_buddy_block_size(mm, block))
> + return 0;
> +
> + list_del(&block->link);
> + mark_free(mm, block);
> + mm->avail += drm_buddy_block_size(mm, block);
> +
> + /* Prevent recursively freeing this node */
> + parent = block->parent;
> + block->parent = NULL;
> +
> + new_start = drm_buddy_block_offset(block);
> + list_add(&block->tmp_link, &dfs);
> + err = __alloc_range(mm, &dfs, new_start, new_size, blocks);
> + if (err) {
> + mark_allocated(block);
> + mm->avail -= drm_buddy_block_size(mm, block);
> + list_add(&block->link, blocks);
> + }
> +
> + block->parent = parent;
> + return err;
> +}
> +EXPORT_SYMBOL(drm_buddy_block_trim);
> +
> /**
> * drm_buddy_alloc_blocks - allocate power-of-two blocks
> *
> diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
> index 3662434b64bb..53eb100688a6 100644
> --- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
> +++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
> @@ -97,6 +97,16 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
> if (unlikely(err))
> goto err_free_blocks;
>
> + if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
> + u64 original_size = (u64)bman_res->base.num_pages << PAGE_SHIFT;
> +
> + mutex_lock(&bman->lock);
> + drm_buddy_block_trim(mm,
> + original_size,
> + &bman_res->blocks);
> + mutex_unlock(&bman->lock);
> + }
> +
> *res = &bman_res->base;
> return 0;
>
> diff --git a/include/drm/drm_buddy.h b/include/drm/drm_buddy.h
> index 424fc443115e..17ca928fce8e 100644
> --- a/include/drm/drm_buddy.h
> +++ b/include/drm/drm_buddy.h
> @@ -145,6 +145,10 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
> struct list_head *blocks,
> unsigned long flags);
>
> +int drm_buddy_block_trim(struct drm_buddy *mm,
> + u64 new_size,
> + struct list_head *blocks);
> +
> void drm_buddy_free_block(struct drm_buddy *mm, struct drm_buddy_block *block);
>
> void drm_buddy_free_list(struct drm_buddy *mm, struct list_head *objects);
>
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