[PATCH v2 3/3] drm/amdgpu: allow temporary GTT allocation under memory pressure

[Christian König]

On which branch are you working? I have problems applying that one to 
amd-staging-drm-next.

Christian.

Am 31.05.21 um 10:22 schrieb Lang Yu:
> Currently, we have a limitted GTT memory size and need a bounce buffer
> when doing buffer migration between VRAM and SYSTEM domain.
>
> The problem is under GTT memory pressure we can't do buffer migration
> between VRAM and SYSTEM domain. But in some cases we really need that.
> Eespecially when validating a VRAM backing store BO which resides in
> SYSTEM domain.
>
> To solve the problem, we allow temporary GTT allocation under memory
> pressure and do the following:
>
> 1. Change mgr->available into mgr->used (invert the value).
> 2. Always account all GTT BOs to the used space.
> 3. Only when it is not a temporary allocation bail out.
>
> v2: still account temporary GTT allocations
>
> Signed-off-by: Lang Yu <Lang.Yu at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c | 27 ++++++++++-----------
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c     |  4 ++-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h     |  2 +-
>   3 files changed, 17 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
> index 8860545344c7..393f55f412b7 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gtt_mgr.c
> @@ -111,14 +111,11 @@ static int amdgpu_gtt_mgr_new(struct ttm_resource_manager *man,
>   	struct amdgpu_gtt_node *node;
>   	int r;
>   
> -	spin_lock(&mgr->lock);
> -	if ((&tbo->mem == mem || tbo->mem.mem_type != TTM_PL_TT) &&
> -	    atomic64_read(&mgr->available) < mem->num_pages) {
> -		spin_unlock(&mgr->lock);
> +	if ((atomic64_add_return(mem->num_pages, &mgr->used) > man->size) &&
> +		!(mem->placement & TTM_PL_FLAG_TEMPORARY)) {
> +		atomic64_sub(mem->num_pages, &mgr->used);
>   		return -ENOSPC;
>   	}
> -	atomic64_sub(mem->num_pages, &mgr->available);
> -	spin_unlock(&mgr->lock);
>   
>   	if (!place->lpfn) {
>   		mem->mm_node = NULL;
> @@ -152,7 +149,7 @@ static int amdgpu_gtt_mgr_new(struct ttm_resource_manager *man,
>   	kfree(node);
>   
>   err_out:
> -	atomic64_add(mem->num_pages, &mgr->available);
> +	atomic64_sub(mem->num_pages, &mgr->used);
>   
>   	return r;
>   }
> @@ -178,7 +175,7 @@ static void amdgpu_gtt_mgr_del(struct ttm_resource_manager *man,
>   		kfree(node);
>   	}
>   
> -	atomic64_add(mem->num_pages, &mgr->available);
> +	atomic64_sub(mem->num_pages, &mgr->used);
>   }
>   
>   /**
> @@ -191,9 +188,8 @@ static void amdgpu_gtt_mgr_del(struct ttm_resource_manager *man,
>   uint64_t amdgpu_gtt_mgr_usage(struct ttm_resource_manager *man)
>   {
>   	struct amdgpu_gtt_mgr *mgr = to_gtt_mgr(man);
> -	s64 result = man->size - atomic64_read(&mgr->available);
>   
> -	return (result > 0 ? result : 0) * PAGE_SIZE;
> +	return atomic64_read(&mgr->used) * PAGE_SIZE;
>   }
>   
>   /**
> @@ -234,14 +230,17 @@ static void amdgpu_gtt_mgr_debug(struct ttm_resource_manager *man,
>   				 struct drm_printer *printer)
>   {
>   	struct amdgpu_gtt_mgr *mgr = to_gtt_mgr(man);
> +	uint64_t used, used_pages;
>   
>   	spin_lock(&mgr->lock);
>   	drm_mm_print(&mgr->mm, printer);
>   	spin_unlock(&mgr->lock);
>   
> -	drm_printf(printer, "man size:%llu pages, gtt available:%lld pages, usage:%lluMB\n",
> -		   man->size, (u64)atomic64_read(&mgr->available),
> -		   amdgpu_gtt_mgr_usage(man) >> 20);
> +	used = amdgpu_gtt_mgr_usage(man);
> +	used_pages = used/PAGE_SIZE;
> +
> +	drm_printf(printer, "man size:%llu pages,  gtt available:%lld pages, usage:%lluMB\n",
> +		man->size, used_pages > man->size ? 0 : man->size - used_pages, used >> 20);
>   }
>   
>   static const struct ttm_resource_manager_func amdgpu_gtt_mgr_func = {
> @@ -274,7 +273,7 @@ int amdgpu_gtt_mgr_init(struct amdgpu_device *adev, uint64_t gtt_size)
>   	size = (adev->gmc.gart_size >> PAGE_SHIFT) - start;
>   	drm_mm_init(&mgr->mm, start, size);
>   	spin_lock_init(&mgr->lock);
> -	atomic64_set(&mgr->available, gtt_size >> PAGE_SHIFT);
> +	atomic64_set(&mgr->used, 0);
>   
>   	ret = device_create_file(adev->dev, &dev_attr_mem_info_gtt_total);
>   	if (ret) {
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> index c0aef327292a..129d39392859 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
> @@ -152,9 +152,11 @@ static void amdgpu_evict_flags(struct ttm_buffer_object *bo,
>   			abo->placements[0].lpfn = 0;
>   			abo->placement.busy_placement = &abo->placements[1];
>   			abo->placement.num_busy_placement = 1;
> +			abo->placements[1].flags |= TTM_PL_FLAG_TEMPORARY;
>   		} else {
>   			/* Move to GTT memory */
>   			amdgpu_bo_placement_from_domain(abo, AMDGPU_GEM_DOMAIN_GTT);
> +			abo->placements[0].flags |= TTM_PL_FLAG_TEMPORARY;
>   		}
>   		break;
>   	case TTM_PL_TT:
> @@ -538,7 +540,7 @@ static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
>   			hop->fpfn = 0;
>   			hop->lpfn = 0;
>   			hop->mem_type = TTM_PL_TT;
> -			hop->flags = 0;
> +			hop->flags |= TTM_PL_FLAG_TEMPORARY;
>   			return -EMULTIHOP;
>   		}
>   
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
> index 2877a924086f..26b67af00550 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
> @@ -52,7 +52,7 @@ struct amdgpu_gtt_mgr {
>   	struct ttm_resource_manager manager;
>   	struct drm_mm mm;
>   	spinlock_t lock;
> -	atomic64_t available;
> +	atomic64_t used;
>   };
>   
>   struct amdgpu_preempt_mgr {