On 04/01/22 7:41 pm, Matthew Auld wrote:
> On 26/12/2021 22:24, 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
>>
>> Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@xxxxxxx>
>> ---
>> drivers/gpu/drm/drm_buddy.c | 61 +++++++++++++++++++
>> drivers/gpu/drm/i915/i915_ttm_buddy_manager.c | 8 +++
>> include/drm/drm_buddy.h | 4 ++
>> 3 files changed, 73 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
>> index eddc1eeda02e..855afcaf7edd 100644
>> --- a/drivers/gpu/drm/drm_buddy.c
>> +++ b/drivers/gpu/drm/drm_buddy.c
>> @@ -538,6 +538,67 @@ static int __drm_buddy_alloc_range(struct drm_buddy_mm *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
>> + *
>> + * 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.
>> + */
>> +void drm_buddy_block_trim(struct drm_buddy_mm *mm,
>> + u64 new_size,
>> + struct list_head *blocks)
>
> It might be better to just return the error, and let the user decide if
> they want to ignore it? Also we might want some kind of unit test for
> this, so having an actual return value might be useful there.
>
sure will revert it
>> +{
>> + struct drm_buddy_block *parent;
>> + struct drm_buddy_block *block;
>> + LIST_HEAD(dfs);
>> + u64 new_start;
>> + int err;
>> +
>> + if (!list_is_singular(blocks))
>> + return;
>> +
>> + block = list_first_entry(blocks,
>> + struct drm_buddy_block,
>> + link);
>> +
>> + if (!drm_buddy_block_is_allocated(block))
>> + return;
>> +
>> + if (new_size > drm_buddy_block_size(mm, block))
>> + return;
>> +
>> + if (!new_size && !IS_ALIGNED(new_size, mm->chunk_size))
>> + return;
>> +
>> + if (new_size == drm_buddy_block_size(mm, block))
>> + return;
>> +
>> + 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;
>> +}
>> +EXPORT_SYMBOL(drm_buddy_block_trim);
>> +
>> /**
>> * drm_buddy_alloc - 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 7c58efb60dba..05f924f32e96 100644
>> --- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
>> +++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
>> @@ -97,6 +97,14 @@ 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) {
>> + mutex_lock(&bman->lock);
>> + drm_buddy_block_trim(mm,
>> + (u64)n_pages << PAGE_SHIFT,
>
> AFAIK, n_pages has already been rounded up to the next power-of-two
> here, so this becomes a noop. I assume we need to use the "original"
> size here?
>
ah yes..missed it, will change as below
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);
>> + &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 f573b02304f4..703866a87939 100644
>> --- a/include/drm/drm_buddy.h
>> +++ b/include/drm/drm_buddy.h
>> @@ -146,6 +146,10 @@ int drm_buddy_alloc(struct drm_buddy_mm *mm,
>> struct list_head *blocks,
>> unsigned long flags);
>>
>> +void drm_buddy_block_trim(struct drm_buddy_mm *mm,
>> + u64 new_size,
>> + struct list_head *blocks);
>> +
>> void drm_buddy_free(struct drm_buddy_mm *mm, struct drm_buddy_block *block);
>>
>> void drm_buddy_free_list(struct drm_buddy_mm *mm, struct list_head *objects);
>>
