[PATCH v3 2/6] drm: improve drm_buddy_alloc function
Arunpravin
arunpravin.paneerselvam at amd.com
Tue Nov 23 22:39:58 UTC 2021
On 18/11/21 12:09 am, Matthew Auld wrote:
> On 16/11/2021 20:18, Arunpravin wrote:
>> - Make drm_buddy_alloc a single function to handle
>> range allocation and non-range allocation demands
>>
>> - Implemented a new function alloc_range() which allocates
>> the requested power-of-two block comply with range limitations
>>
>> - Moved order computation and memory alignment logic from
>> i915 driver to drm buddy
>>
>> v2:
>> merged below changes to keep the build unbroken
>> - drm_buddy_alloc_range() becomes obsolete and may be removed
>> - enable ttm range allocation (fpfn / lpfn) support in i915 driver
>> - apply enhanced drm_buddy_alloc() function to i915 driver
>>
>> v3(Matthew Auld):
>> - Fix alignment issues and remove unnecessary list_empty check
>> - add more validation checks for input arguments
>> - make alloc_range() block allocations as bottom-up
>> - optimize order computation logic
>> - replace uint64_t with u64, which is preferred in the kernel
>>
>> Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam at amd.com>
>> ---
>> drivers/gpu/drm/drm_buddy.c | 259 ++++++++++--------
>> drivers/gpu/drm/i915/i915_ttm_buddy_manager.c | 69 ++---
>> drivers/gpu/drm/i915/i915_ttm_buddy_manager.h | 2 +
>> include/drm/drm_buddy.h | 22 +-
>> 4 files changed, 203 insertions(+), 149 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
>> index 39eb1d224bec..c9b18a29f8d1 100644
>> --- a/drivers/gpu/drm/drm_buddy.c
>> +++ b/drivers/gpu/drm/drm_buddy.c
>> @@ -274,63 +274,6 @@ void drm_buddy_free_list(struct drm_buddy_mm *mm, struct list_head *objects)
>> }
>> EXPORT_SYMBOL(drm_buddy_free_list);
>>
>> -/**
>> - * drm_buddy_alloc - allocate power-of-two blocks
>> - *
>> - * @mm: DRM buddy manager to allocate from
>> - * @order: size of the allocation
>> - *
>> - * The order value here translates to:
>> - *
>> - * 0 = 2^0 * mm->chunk_size
>> - * 1 = 2^1 * mm->chunk_size
>> - * 2 = 2^2 * mm->chunk_size
>> - *
>> - * Returns:
>> - * allocated ptr to the &drm_buddy_block on success
>> - */
>> -struct drm_buddy_block *
>> -drm_buddy_alloc(struct drm_buddy_mm *mm, unsigned int order)
>> -{
>> - struct drm_buddy_block *block = NULL;
>> - unsigned int i;
>> - int err;
>> -
>> - for (i = order; i <= mm->max_order; ++i) {
>> - block = list_first_entry_or_null(&mm->free_list[i],
>> - struct drm_buddy_block,
>> - link);
>> - if (block)
>> - break;
>> - }
>> -
>> - if (!block)
>> - return ERR_PTR(-ENOSPC);
>> -
>> - BUG_ON(!drm_buddy_block_is_free(block));
>> -
>> - while (i != order) {
>> - err = split_block(mm, block);
>> - if (unlikely(err))
>> - goto out_free;
>> -
>> - /* Go low */
>> - block = block->left;
>> - i--;
>> - }
>> -
>> - mark_allocated(block);
>> - mm->avail -= drm_buddy_block_size(mm, block);
>> - kmemleak_update_trace(block);
>> - return block;
>> -
>> -out_free:
>> - if (i != order)
>> - __drm_buddy_free(mm, block);
>> - return ERR_PTR(err);
>> -}
>> -EXPORT_SYMBOL(drm_buddy_alloc);
>> -
>> static inline bool overlaps(u64 s1, u64 e1, u64 s2, u64 e2)
>> {
>> return s1 <= e2 && e1 >= s2;
>> @@ -341,52 +284,22 @@ static inline bool contains(u64 s1, u64 e1, u64 s2, u64 e2)
>> return s1 <= s2 && e1 >= e2;
>> }
>>
>> -/**
>> - * drm_buddy_alloc_range - allocate range
>> - *
>> - * @mm: DRM buddy manager to allocate from
>> - * @blocks: output list head to add allocated blocks
>> - * @start: start of the allowed range for this block
>> - * @size: size of the allocation
>> - *
>> - * Intended for pre-allocating portions of the address space, for example to
>> - * reserve a block for the initial framebuffer or similar, hence the expectation
>> - * here is that drm_buddy_alloc() is still the main vehicle for
>> - * allocations, so if that's not the case then the drm_mm range allocator is
>> - * probably a much better fit, and so you should probably go use that instead.
>> - *
>> - * Note that it's safe to chain together multiple alloc_ranges
>> - * with the same blocks list
>> - *
>> - * Returns:
>> - * 0 on success, error code on failure.
>> - */
>> -int drm_buddy_alloc_range(struct drm_buddy_mm *mm,
>> - struct list_head *blocks,
>> - u64 start, u64 size)
>> +static struct drm_buddy_block *
>> +alloc_range(struct drm_buddy_mm *mm,
>> + u64 start, u64 end,
>> + unsigned int order)
>> {
>> struct drm_buddy_block *block;
>> struct drm_buddy_block *buddy;
>> - LIST_HEAD(allocated);
>> LIST_HEAD(dfs);
>> - u64 end;
>> int err;
>> int i;
>>
>> - if (size < mm->chunk_size)
>> - return -EINVAL;
>> -
>> - if (!IS_ALIGNED(size | start, mm->chunk_size))
>> - return -EINVAL;
>> -
>> - if (range_overflows(start, size, mm->size))
>> - return -EINVAL;
>> + end = end - 1;
>>
>> for (i = 0; i < mm->n_roots; ++i)
>> list_add_tail(&mm->roots[i]->tmp_link, &dfs);
>>
>> - end = start + size - 1;
>> -
>> do {
>> u64 block_start;
>> u64 block_end;
>> @@ -399,26 +312,26 @@ int drm_buddy_alloc_range(struct drm_buddy_mm *mm,
>>
>> list_del(&block->tmp_link);
>>
>> + if (drm_buddy_block_order(block) < order)
>> + continue;
>> +
>> block_start = drm_buddy_block_offset(block);
>> block_end = block_start + drm_buddy_block_size(mm, block) - 1;
>>
>> if (!overlaps(start, end, block_start, block_end))
>> continue;
>>
>> - if (drm_buddy_block_is_allocated(block)) {
>> - err = -ENOSPC;
>> - goto err_free;
>> - }
>> + if (drm_buddy_block_is_allocated(block))
>> + continue;
>>
>> - if (contains(start, end, block_start, block_end)) {
>> - if (!drm_buddy_block_is_free(block)) {
>> - err = -ENOSPC;
>> - goto err_free;
>> - }
>> + if (contains(start, end, block_start, block_end) &&
>> + order == drm_buddy_block_order(block)) {
>> + /*
>> + * Find the free block within the range.
>> + */
>> + if (drm_buddy_block_is_free(block))
>> + return block;
>
> AFAIK this is still randomly ordered when dealing with actual range
> allocation. Maybe I'm missing something, but it looks like we are just
> repeatedly picking the largest order that fits in the remaining number
> of pages, but it might be the case that the smallest block is for
> example at the start of the range, depending on the layout of the
> address space, which would then only get allocated last.
>
> I think I mentioned this before, but most of the block_trim() looks to
> already do what we want for this case, and could maybe be factored out,
> since that is also just another range allocation, except we start with
> one root node for our "dfs" search.
>
> Maybe something like:
>
> drm_buddy_trim(block, new_size...)
> {
> ....
> mark_free(block);
> list_add(&block->tmp_link, &dfs);
> err = __alloc_range(mm, &dfs, block->start, new_size, ...);
> if (err)
> ....
> }
>
> __drm_buddy_alloc_range(start, size, blocks)
> {
> for_each_root()
> list_add(&root->tmp_link, &dfs);
>
> err = __alloc_range(mm, &dfs, start, size, ...);
> if (err)
> ....
> }
>
> drm_buddy_alloc(...)
> {
> /* Actual range allocation */
> if (start + size == end)
> return __drm_buddy_alloc_range(...);
> ....
> }
>
> And then have something different for the alloc_range_bias()?
>
Yes, we will have a common function __alloc_range() which does the range
allocation for block_trim() and __drm_buddy_alloc_range() (actual range
allocation).
And, I understood that we keep the alloc_range() implementation for end
bias allocations?
>>
>> - mark_allocated(block);
>> - mm->avail -= drm_buddy_block_size(mm, block);
>> - list_add_tail(&block->link, &allocated);
>> continue;
>> }
>>
>> @@ -432,8 +345,7 @@ int drm_buddy_alloc_range(struct drm_buddy_mm *mm,
>> list_add(&block->left->tmp_link, &dfs);
>> } while (1);
>>
>> - list_splice_tail(&allocated, blocks);
>> - return 0;
>> + return ERR_PTR(-ENOSPC);
>>
>> err_undo:
>> /*
>> @@ -446,12 +358,145 @@ int drm_buddy_alloc_range(struct drm_buddy_mm *mm,
>> (drm_buddy_block_is_free(block) &&
>> drm_buddy_block_is_free(buddy)))
>> __drm_buddy_free(mm, block);
>> + return ERR_PTR(err);
>> +}
>> +
>> +static struct drm_buddy_block *
>> +alloc_from_freelist(struct drm_buddy_mm *mm,
>> + unsigned int order,
>> + unsigned long flags)
>> +{
>> + struct drm_buddy_block *block = NULL;
>> + unsigned int i;
>> + int err;
>> +
>> + for (i = order; i <= mm->max_order; ++i) {
>> + block = list_first_entry_or_null(&mm->free_list[i],
>> + struct drm_buddy_block,
>> + link);
>> + if (block)
>> + break;
>> + }
>> +
>> + if (!block)
>> + return ERR_PTR(-ENOSPC);
>> +
>> + BUG_ON(!drm_buddy_block_is_free(block));
>> +
>> + while (i != order) {
>> + err = split_block(mm, block);
>> + if (unlikely(err))
>> + goto err_undo;
>> +
>> + block = block->right;
>> + i--;
>> + }
>> + return block;
>> +
>> +err_undo:
>> + if (i != order)
>> + __drm_buddy_free(mm, block);
>> + return ERR_PTR(err);
>> +}
>> +
>> +/**
>> + * drm_buddy_alloc - allocate power-of-two blocks
>> + *
>> + * @mm: DRM buddy manager to allocate from
>> + * @start: start of the allowed range for this block
>> + * @end: end of the allowed range for this block
>> + * @size: size of the allocation
>> + * @min_page_size: alignment of the allocation
>> + * @blocks: output list head to add allocated blocks
>> + * @flags: DRM_BUDDY_*_ALLOCATION flags
>> + *
>> + * alloc_range() called on range limitations, which traverses
>> + * the tree and returns the desired block.
>> + *
>> + * alloc_from_freelist() called when *no* range restrictions
>> + * are enforced, which picks the block from the freelist.
>> + *
>> + * blocks are allocated in order, the order value here translates to:
>> + *
>> + * 0 = 2^0 * mm->chunk_size
>> + * 1 = 2^1 * mm->chunk_size
>> + * 2 = 2^2 * mm->chunk_size
>> + *
>> + * Returns:
>> + * 0 on success, error code on failure.
>> + */
>> +int drm_buddy_alloc(struct drm_buddy_mm *mm,
>> + u64 start, u64 end, u64 size,
>> + u64 min_page_size,
>> + struct list_head *blocks,
>> + unsigned long flags)
>> +{
>> + struct drm_buddy_block *block = NULL;
>> + unsigned int min_order, order;
>> + unsigned long pages;
>> + LIST_HEAD(allocated);
>> + int err;
>> +
>> + if (size < mm->chunk_size)
>> + return -EINVAL;
>> +
>> + if (min_page_size < mm->chunk_size)
>> + return -EINVAL;
>> +
>> + if (!is_power_of_2(min_page_size))
>> + return -EINVAL;
>> +
>> + if (!IS_ALIGNED(start | end | size, mm->chunk_size))
>> + return -EINVAL;
>> +
>> + if (check_range_overflow(start, end, size, mm->size))
>> + return -EINVAL;
>> +
>> + pages = size >> ilog2(mm->chunk_size);
>> + order = fls(pages) - 1;
>> + min_order = ilog2(min_page_size) - ilog2(mm->chunk_size);
>> +
>> + do {
>> + order = min(order, (unsigned int)fls(pages) - 1);
>> + BUG_ON(order > mm->max_order);
>> + BUG_ON(order < min_order);
>> +
>> + do {
>> + if (flags & DRM_BUDDY_RANGE_ALLOCATION)
>> + /* Allocate traversing within the range */
>> + block = alloc_range(mm, start, end, order);
>> + else
>> + /* Allocate from freelist */
>> + block = alloc_from_freelist(mm, order, flags);
>> +
>> + if (!IS_ERR(block))
>> + break;
>> +
>> + if (order-- == min_order) {
>> + err = -ENOSPC;
>> + goto err_free;
>> + }
>> + } while (1);
>> +
>> + mark_allocated(block);
>> + mm->avail -= drm_buddy_block_size(mm, block);
>> + kmemleak_update_trace(block);
>> + list_add_tail(&block->link, &allocated);
>> +
>> + pages -= BIT(order);
>> +
>> + if (!pages)
>> + break;
>> + } while (1);
>> +
>> + list_splice_tail(&allocated, blocks);
>> + return 0;
>>
>> err_free:
>> drm_buddy_free_list(mm, &allocated);
>> return err;
>> }
>> -EXPORT_SYMBOL(drm_buddy_alloc_range);
>> +EXPORT_SYMBOL(drm_buddy_alloc);
>>
>> /**
>> * drm_buddy_block_print - print block information
>> diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
>> index c4b70cb8c248..9e3d130c3f42 100644
>> --- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
>> +++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
>> @@ -36,13 +36,14 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
>> struct i915_ttm_buddy_manager *bman = to_buddy_manager(man);
>> struct i915_ttm_buddy_resource *bman_res;
>> struct drm_buddy_mm *mm = &bman->mm;
>> - unsigned long n_pages;
>> - unsigned int min_order;
>> + unsigned long n_pages, lpfn;
>> u64 min_page_size;
>> u64 size;
>> int err;
>>
>> - GEM_BUG_ON(place->fpfn || place->lpfn);
>> + lpfn = place->lpfn;
>> + if (!lpfn)
>> + lpfn = man->size;
>>
>> bman_res = kzalloc(sizeof(*bman_res), GFP_KERNEL);
>> if (!bman_res)
>> @@ -52,6 +53,9 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
>> INIT_LIST_HEAD(&bman_res->blocks);
>> bman_res->mm = mm;
>>
>> + if (place->fpfn || lpfn != man->size)
>> + bman_res->flags |= DRM_BUDDY_RANGE_ALLOCATION;
>> +
>> GEM_BUG_ON(!bman_res->base.num_pages);
>> size = bman_res->base.num_pages << PAGE_SHIFT;
>>
>> @@ -60,10 +64,16 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
>> min_page_size = bo->page_alignment << PAGE_SHIFT;
>>
>> GEM_BUG_ON(min_page_size < mm->chunk_size);
>> - min_order = ilog2(min_page_size) - ilog2(mm->chunk_size);
>> +
>> if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
>> + unsigned long pages;
>> +
>> size = roundup_pow_of_two(size);
>> - min_order = ilog2(size) - ilog2(mm->chunk_size);
>> + min_page_size = size;
>> +
>> + pages = size >> ilog2(mm->chunk_size);
>> + if (pages > lpfn)
>> + lpfn = pages;
>> }
>>
>> if (size > mm->size) {
>> @@ -73,34 +83,16 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
>>
>> n_pages = size >> ilog2(mm->chunk_size);
>>
>> - do {
>> - struct drm_buddy_block *block;
>> - unsigned int order;
>> -
>> - order = fls(n_pages) - 1;
>> - GEM_BUG_ON(order > mm->max_order);
>> - GEM_BUG_ON(order < min_order);
>> -
>> - do {
>> - mutex_lock(&bman->lock);
>> - block = drm_buddy_alloc(mm, order);
>> - mutex_unlock(&bman->lock);
>> - if (!IS_ERR(block))
>> - break;
>> -
>> - if (order-- == min_order) {
>> - err = -ENOSPC;
>> - goto err_free_blocks;
>> - }
>> - } while (1);
>> -
>> - n_pages -= BIT(order);
>> -
>> - list_add_tail(&block->link, &bman_res->blocks);
>> -
>> - if (!n_pages)
>> - break;
>> - } while (1);
>> + mutex_lock(&bman->lock);
>> + err = drm_buddy_alloc(mm, (u64)place->fpfn << PAGE_SHIFT,
>> + (u64)place->lpfn << PAGE_SHIFT,
>> + (u64)n_pages << PAGE_SHIFT,
>> + min_page_size,
>> + &bman_res->blocks,
>> + bman_res->flags);
>> + mutex_unlock(&bman->lock);
>> + if (unlikely(err))
>> + goto err_free_blocks;
>>
>> *res = &bman_res->base;
>> return 0;
>> @@ -266,10 +258,19 @@ int i915_ttm_buddy_man_reserve(struct ttm_resource_manager *man,
>> {
>> struct i915_ttm_buddy_manager *bman = to_buddy_manager(man);
>> struct drm_buddy_mm *mm = &bman->mm;
>> + unsigned long flags = 0;
>> + u64 min_size;
>> int ret;
>>
>> + min_size = size;
>> + flags |= DRM_BUDDY_RANGE_ALLOCATION;
>> +
>> mutex_lock(&bman->lock);
>> - ret = drm_buddy_alloc_range(mm, &bman->reserved, start, size);
>> + ret = drm_buddy_alloc(mm, start,
>> + start + size,
>> + size, min_size,
>
> min_page_size = min_size = size. I don't think we want that here. Also
> the size here might not be power of two. I guess we need to use
> chunk_size here instead?
ok, we will use chunk_size here.
>
>> + &bman->reserved,
>> + flags);
>> mutex_unlock(&bman->lock);
>>
>> return ret;
>> diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
>> index fa644b512c2e..5ba490875f66 100644
>> --- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
>> +++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
>> @@ -20,6 +20,7 @@ struct drm_buddy_mm;
>> *
>> * @base: struct ttm_resource base class we extend
>> * @blocks: the list of struct i915_buddy_block for this resource/allocation
>> + * @flags: DRM_BUDDY_*_ALLOCATION flags
>> * @mm: the struct i915_buddy_mm for this resource
>> *
>> * Extends the struct ttm_resource to manage an address space allocation with
>> @@ -28,6 +29,7 @@ struct drm_buddy_mm;
>> struct i915_ttm_buddy_resource {
>> struct ttm_resource base;
>> struct list_head blocks;
>> + unsigned long flags;
>> struct drm_buddy_mm *mm;
>> };
>>
>> diff --git a/include/drm/drm_buddy.h b/include/drm/drm_buddy.h
>> index 5ce3fc702f80..2ec3cbc9d5d7 100644
>> --- a/include/drm/drm_buddy.h
>> +++ b/include/drm/drm_buddy.h
>> @@ -13,15 +13,22 @@
>>
>> #include <drm/drm_print.h>
>>
>> -#define range_overflows(start, size, max) ({ \
>> +#define check_range_overflow(start, end, size, max) ({ \
>> typeof(start) start__ = (start); \
>> + typeof(end) end__ = (end);\
>> typeof(size) size__ = (size); \
>> typeof(max) max__ = (max); \
>> (void)(&start__ == &size__); \
>> (void)(&start__ == &max__); \
>> - start__ >= max__ || size__ > max__ - start__; \
>> + (void)(&start__ == &end__); \
>> + (void)(&end__ == &size__); \
>> + (void)(&end__ == &max__); \
>> + start__ >= max__ || end__ > max__ || \
>> + size__ > end__ - start__; \
>> })
>>
>> +#define DRM_BUDDY_RANGE_ALLOCATION (1 << 0)
>> +
>> struct drm_buddy_block {
>> #define DRM_BUDDY_HEADER_OFFSET GENMASK_ULL(63, 12)
>> #define DRM_BUDDY_HEADER_STATE GENMASK_ULL(11, 10)
>> @@ -131,12 +138,11 @@ int drm_buddy_init(struct drm_buddy_mm *mm, u64 size, u64 chunk_size);
>>
>> void drm_buddy_fini(struct drm_buddy_mm *mm);
>>
>> -struct drm_buddy_block *
>> -drm_buddy_alloc(struct drm_buddy_mm *mm, unsigned int order);
>> -
>> -int drm_buddy_alloc_range(struct drm_buddy_mm *mm,
>> - struct list_head *blocks,
>> - u64 start, u64 size);
>> +int drm_buddy_alloc(struct drm_buddy_mm *mm,
>> + u64 start, u64 end, u64 size,
>> + u64 min_page_size,
>> + struct list_head *blocks,
>> + unsigned long flags);
>>
>> void drm_buddy_free(struct drm_buddy_mm *mm, struct drm_buddy_block *block);
>>
>>
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