> -----Original Message-----
> From: amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Matthew Auld
> Sent: Thursday, January 20, 2022 11:05 PM
> To: Paneer Selvam, Arunpravin <Arunpravin.PaneerSelvam@xxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx; intel-gfx@xxxxxxxxxxxxxxxxxxxxx; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: Deucher, Alexander <Alexander.Deucher@xxxxxxx>; tzimmermann@xxxxxxx; jani.nikula@xxxxxxxxxxxxxxx; Koenig, Christian <Christian.Koenig@xxxxxxx>; daniel@xxxxxxxx
> Subject: Re: [PATCH v9 4/6] drm: implement a method to free unused pages
>
> 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@xxxxxxxxx>
>>
>> Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@xxxxxxx>
>> ---
>> 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,
Good to hear its running on DG1, all changes are added to v10. working
on moving i915 buddy selftests into drm selftest folder, I will add a
new unit test case for trim function
> Reviewed-by: Matthew Auld <matthew.auld@xxxxxxxxx>
>
>> +
>> + 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);
>>
