Re: [Intel-gfx] [PATCH v11] drm/amdgpu: add drm buddy support to amdgpu

[Arunpravin Paneer Selvam <arunpravin.paneerselvam@amd.com>]

> -----Original Message-----
> From: amd-gfx <amd-gfx-bounces@lists.freedesktop.org> On Behalf Of Christian König
> Sent: Wednesday, March 23, 2022 1:07 PM
> To: Paneer Selvam, Arunpravin <Arunpravin.PaneerSelvam@amd.com>; intel-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org; amd-gfx@lists.freedesktop.org
> Cc: Deucher, Alexander <Alexander.Deucher@amd.com>; matthew.auld@intel.com; daniel@ffwll.ch; Koenig, Christian <Christian.Koenig@amd.com>
> Subject: Re: [PATCH v11] drm/amdgpu: add drm buddy support to amdgpu
> 
> Am 23.03.22 um 07:25 schrieb Arunpravin Paneer Selvam:
>> [SNIP]
>> @@ -415,48 +409,86 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>>   		goto error_fini;
>>   	}
>>   
>> -	mode = DRM_MM_INSERT_BEST;
>> +	INIT_LIST_HEAD(&node->blocks);
>> +
>>   	if (place->flags & TTM_PL_FLAG_TOPDOWN)
>> -		mode = DRM_MM_INSERT_HIGH;
>> +		node->flags |= DRM_BUDDY_TOPDOWN_ALLOCATION;
>>   
>> -	pages_left = node->base.num_pages;
>> +	if (place->fpfn || lpfn != man->size >> PAGE_SHIFT)
>> +		/* Allocate blocks in desired range */
>> +		node->flags |= DRM_BUDDY_RANGE_ALLOCATION;
>>   
>> -	/* Limit maximum size to 2GB due to SG table limitations */
>> -	pages = min(pages_left, 2UL << (30 - PAGE_SHIFT));
>> +	BUG_ON(!node->base.num_pages);
> 
> Please drop this BUG_ON(). This is not something which prevents further data corruption, so the BUG_ON() is not justified.

ok
> 
>> +	pages_left = node->base.num_pages;
>>   
>>   	i = 0;
>> -	spin_lock(&mgr->lock);
>>   	while (pages_left) {
>> -		uint32_t alignment = tbo->page_alignment;
>> +		if (tbo->page_alignment)
>> +			min_page_size = tbo->page_alignment << PAGE_SHIFT;
>> +		else
>> +			min_page_size = mgr->default_page_size;
> 
> The handling here looks extremely awkward to me.
> 
> min_page_size should be determined outside of the loop, based on default_page_size, alignment and contiguous flag.
I kept min_page_size determine logic inside the loop for cases 2GiB+
requirements, Since now we are round up the size to the required
alignment, I modified the min_page_size determine logic outside of the
loop in v12. Please review.
> 
> Then why do you drop the lock and grab it again inside the loop? And what is "i" actually good for?
modified the lock/unlock placement in v12.

"i" is to track when there is 2GiB+ contiguous allocation request, first
we allocate 2GiB (due to SG table limit) continuously and the remaining
pages in the next iteration, hence this request can't be a continuous.
To set the placement flag we make use of "i" value. In our case "i"
value becomes 2 and we don't set the below flag.
node->base.placement |= TTM_PL_FLAG_CONTIGUOUS;

If we don't get such requests, I will remove "i".

>



>> +
>> +		/* Limit maximum size to 2GB due to SG table limitations */
>> +		pages = min(pages_left, 2UL << (30 - PAGE_SHIFT));
>>   
>>   		if (pages >= pages_per_node)
>> -			alignment = pages_per_node;
>> -
>> -		r = drm_mm_insert_node_in_range(mm, &node->mm_nodes[i], pages,
>> -						alignment, 0, place->fpfn,
>> -						lpfn, mode);
>> -		if (unlikely(r)) {
>> -			if (pages > pages_per_node) {
>> -				if (is_power_of_2(pages))
>> -					pages = pages / 2;
>> -				else
>> -					pages = rounddown_pow_of_two(pages);
>> -				continue;
>> -			}
>> -			goto error_free;
>> +			min_page_size = pages_per_node << PAGE_SHIFT;
>> +
>> +		if (!is_contiguous && !IS_ALIGNED(pages, min_page_size >> PAGE_SHIFT))
>> +			is_contiguous = 1;
>> +
>> +		if (is_contiguous) {
>> +			pages = roundup_pow_of_two(pages);
>> +			min_page_size = pages << PAGE_SHIFT;
>> +
>> +			if (pages > lpfn)
>> +				lpfn = pages;
>>   		}
>>   
>> -		vis_usage += amdgpu_vram_mgr_vis_size(adev, &node->mm_nodes[i]);
>> -		amdgpu_vram_mgr_virt_start(&node->base, &node->mm_nodes[i]);
>> -		pages_left -= pages;
>> +		BUG_ON(min_page_size < mm->chunk_size);
>> +
>> +		mutex_lock(&mgr->lock);
>> +		r = drm_buddy_alloc_blocks(mm, (u64)place->fpfn << PAGE_SHIFT,
>> +					   (u64)lpfn << PAGE_SHIFT,
>> +					   (u64)pages << PAGE_SHIFT,
>> +					   min_page_size,
>> +					   &node->blocks,
>> +					   node->flags);
>> +		mutex_unlock(&mgr->lock);
>> +		if (unlikely(r))
>> +			goto error_free_blocks;
>> +
>>   		++i;
>>   
>>   		if (pages > pages_left)
>> -			pages = pages_left;
>> +			pages_left = 0;
>> +		else
>> +			pages_left -= pages;
>>   	}
>> -	spin_unlock(&mgr->lock);
>>   
>> -	if (i == 1)
>> +	/* Free unused pages for contiguous allocation */
>> +	if (is_contiguous) {
> 
> Well that looks really odd, why is trimming not part of
> drm_buddy_alloc_blocks() ?
we didn't place trim function part of drm_buddy_alloc_blocks since we
thought this function can be a generic one and it can be used by any
other application as well. For example, now we are using it for trimming
the last block in case of size non-alignment with min_page_size.
> 
>> +		u64 actual_size = (u64)node->base.num_pages << PAGE_SHIFT;
>> +
>> +		mutex_lock(&mgr->lock);
>> +		drm_buddy_block_trim(mm,
>> +				     actual_size,
>> +				     &node->blocks);
> 
> Why is the drm_buddy_block_trim() function given all the blocks and not just the last one?
modified in v12.
> 
> Regards,
> Christian.
> 
>> +		mutex_unlock(&mgr->lock);
>> +	}
>> +
>> +	list_for_each_entry(block, &node->blocks, link)
>> +		vis_usage += amdgpu_vram_mgr_vis_size(adev, block);
>> +
>> +	block = amdgpu_vram_mgr_first_block(&node->blocks);
>> +	if (!block) {
>> +		r = -EINVAL;
>> +		goto error_fini;
>> +	}
>> +
>> +	node->base.start = amdgpu_node_start(block) >> PAGE_SHIFT;
>> +
>> +	if (i == 1 && is_contiguous)
>>   		node->base.placement |= TTM_PL_FLAG_CONTIGUOUS;
>>   
>>   	if (adev->gmc.xgmi.connected_to_cpu) @@ -468,13 +500,13 @@ static 
>> int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>>   	*res = &node->base;
>>   	return 0;
>>   
>> -error_free:
>> -	while (i--)
>> -		drm_mm_remove_node(&node->mm_nodes[i]);
>> -	spin_unlock(&mgr->lock);
>> +error_free_blocks:
>> +	mutex_lock(&mgr->lock);
>> +	drm_buddy_free_list(mm, &node->blocks);
>> +	mutex_unlock(&mgr->lock);
>>   error_fini:
>>   	ttm_resource_fini(man, &node->base);
>> -	kvfree(node);
>> +	kfree(node);
>>   
>>   	return r;
>>   }
>> @@ -490,27 +522,26 @@ static int amdgpu_vram_mgr_new(struct ttm_resource_manager *man,
>>   static void amdgpu_vram_mgr_del(struct ttm_resource_manager *man,
>>   				struct ttm_resource *res)
>>   {
>> -	struct ttm_range_mgr_node *node = to_ttm_range_mgr_node(res);
>> +	struct amdgpu_vram_mgr_node *node = to_amdgpu_vram_mgr_node(res);
>>   	struct amdgpu_vram_mgr *mgr = to_vram_mgr(man);
>>   	struct amdgpu_device *adev = to_amdgpu_device(mgr);
>> +	struct drm_buddy *mm = &mgr->mm;
>> +	struct drm_buddy_block *block;
>>   	uint64_t vis_usage = 0;
>> -	unsigned i, pages;
>>   
>> -	spin_lock(&mgr->lock);
>> -	for (i = 0, pages = res->num_pages; pages;
>> -	     pages -= node->mm_nodes[i].size, ++i) {
>> -		struct drm_mm_node *mm = &node->mm_nodes[i];
>> +	mutex_lock(&mgr->lock);
>> +	list_for_each_entry(block, &node->blocks, link)
>> +		vis_usage += amdgpu_vram_mgr_vis_size(adev, block);
>>   
>> -		drm_mm_remove_node(mm);
>> -		vis_usage += amdgpu_vram_mgr_vis_size(adev, mm);
>> -	}
>>   	amdgpu_vram_mgr_do_reserve(man);
>> -	spin_unlock(&mgr->lock);
>> +
>> +	drm_buddy_free_list(mm, &node->blocks);
>> +	mutex_unlock(&mgr->lock);
>>   
>>   	atomic64_sub(vis_usage, &mgr->vis_usage);
>>   
>>   	ttm_resource_fini(man, res);
>> -	kvfree(node);
>> +	kfree(node);
>>   }
>>   
>>   /**
>> @@ -648,13 +679,22 @@ static void amdgpu_vram_mgr_debug(struct ttm_resource_manager *man,
>>   				  struct drm_printer *printer)
>>   {
>>   	struct amdgpu_vram_mgr *mgr = to_vram_mgr(man);
>> +	struct drm_buddy *mm = &mgr->mm;
>> +	struct drm_buddy_block *block;
>>   
>>   	drm_printf(printer, "  vis usage:%llu\n",
>>   		   amdgpu_vram_mgr_vis_usage(mgr));
>>   
>> -	spin_lock(&mgr->lock);
>> -	drm_mm_print(&mgr->mm, printer);
>> -	spin_unlock(&mgr->lock);
>> +	mutex_lock(&mgr->lock);
>> +	drm_printf(printer, "default_page_size: %lluKiB\n",
>> +		   mgr->default_page_size >> 10);
>> +
>> +	drm_buddy_print(mm, printer);
>> +
>> +	drm_printf(printer, "reserved:\n");
>> +	list_for_each_entry(block, &mgr->reserved_pages, link)
>> +		drm_buddy_block_print(mm, block, printer);
>> +	mutex_unlock(&mgr->lock);
>>   }
>>   
>>   static const struct ttm_resource_manager_func amdgpu_vram_mgr_func = 
>> { @@ -674,16 +714,21 @@ int amdgpu_vram_mgr_init(struct amdgpu_device *adev)
>>   {
>>   	struct amdgpu_vram_mgr *mgr = &adev->mman.vram_mgr;
>>   	struct ttm_resource_manager *man = &mgr->manager;
>> +	int err;
>>   
>>   	ttm_resource_manager_init(man, &adev->mman.bdev,
>>   				  adev->gmc.real_vram_size);
>>   
>>   	man->func = &amdgpu_vram_mgr_func;
>>   
>> -	drm_mm_init(&mgr->mm, 0, man->size >> PAGE_SHIFT);
>> -	spin_lock_init(&mgr->lock);
>> +	err = drm_buddy_init(&mgr->mm, man->size, PAGE_SIZE);
>> +	if (err)
>> +		return err;
>> +
>> +	mutex_init(&mgr->lock);
>>   	INIT_LIST_HEAD(&mgr->reservations_pending);
>>   	INIT_LIST_HEAD(&mgr->reserved_pages);
>> +	mgr->default_page_size = PAGE_SIZE;
>>   
>>   	ttm_set_driver_manager(&adev->mman.bdev, TTM_PL_VRAM, &mgr->manager);
>>   	ttm_resource_manager_set_used(man, true); @@ -711,16 +756,16 @@ 
>> void amdgpu_vram_mgr_fini(struct amdgpu_device *adev)
>>   	if (ret)
>>   		return;
>>   
>> -	spin_lock(&mgr->lock);
>> +	mutex_lock(&mgr->lock);
>>   	list_for_each_entry_safe(rsv, temp, &mgr->reservations_pending, node)
>>   		kfree(rsv);
>>   
>>   	list_for_each_entry_safe(rsv, temp, &mgr->reserved_pages, node) {
>> -		drm_mm_remove_node(&rsv->mm_node);
>> +		drm_buddy_free_list(&mgr->mm, &rsv->block);
>>   		kfree(rsv);
>>   	}
>> -	drm_mm_takedown(&mgr->mm);
>> -	spin_unlock(&mgr->lock);
>> +	drm_buddy_fini(&mgr->mm);
>> +	mutex_unlock(&mgr->lock);
>>   
>>   	ttm_resource_manager_cleanup(man);
>>   	ttm_set_driver_manager(&adev->mman.bdev, TTM_PL_VRAM, NULL);
>>
>> base-commit: a678f97326454b60ffbbde6abf52d23997d71a27