[PATCH v3 7/8] drm/v3d: Use gemfs/THP in BO creation if available

[Tvrtko Ursulin]

On 21/04/2024 22:44, Maíra Canal wrote:
> Although Big/Super Pages could appear naturally, it would be quite hard
> to have 1MB or 64KB allocated contiguously naturally. Therefore, we can
> force the creation of large pages allocated contiguously by using a
> mountpoint with "huge=within_size" enabled.
> 
> As V3D has a mountpoint with "huge=within_size" (if user has THP enabled),
> use this mountpoint for BO creation if available. This will allow us to create
> large pages allocated contiguously and make use of Big/Super Pages.
> 
> Signed-off-by: Maíra Canal <mcanal at igalia.com>
> ---
>   drivers/gpu/drm/v3d/v3d_bo.c | 21 +++++++++++++++++++--
>   1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/v3d/v3d_bo.c b/drivers/gpu/drm/v3d/v3d_bo.c
> index 79e31c5299b1..16ac26c31c6b 100644
> --- a/drivers/gpu/drm/v3d/v3d_bo.c
> +++ b/drivers/gpu/drm/v3d/v3d_bo.c
> @@ -94,6 +94,7 @@ v3d_bo_create_finish(struct drm_gem_object *obj)
>   	struct v3d_dev *v3d = to_v3d_dev(obj->dev);
>   	struct v3d_bo *bo = to_v3d_bo(obj);
>   	struct sg_table *sgt;
> +	u64 align;
>   	int ret;
>   
>   	/* So far we pin the BO in the MMU for its lifetime, so use
> @@ -103,6 +104,15 @@ v3d_bo_create_finish(struct drm_gem_object *obj)
>   	if (IS_ERR(sgt))
>   		return PTR_ERR(sgt);
>   
> +	if (!v3d->gemfs)
> +		align = SZ_4K;
> +	else if (obj->size >= SZ_1M)
> +		align = SZ_1M;
> +	else if (obj->size >= SZ_64K)
> +		align = SZ_64K;
> +	else
> +		align = SZ_4K;

V3d has one GPU address space, right? I wonder if one day fragmentation 
could become an issue but it's a problem for another day. Patch looks 
fine to me.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>

Regards,

Tvrtko

> +
>   	spin_lock(&v3d->mm_lock);
>   	/* Allocate the object's space in the GPU's page tables.
>   	 * Inserting PTEs will happen later, but the offset is for the
> @@ -110,7 +120,7 @@ v3d_bo_create_finish(struct drm_gem_object *obj)
>   	 */
>   	ret = drm_mm_insert_node_generic(&v3d->mm, &bo->node,
>   					 obj->size >> V3D_MMU_PAGE_SHIFT,
> -					 SZ_4K >> V3D_MMU_PAGE_SHIFT, 0, 0);
> +					 align >> V3D_MMU_PAGE_SHIFT, 0, 0);
>   	spin_unlock(&v3d->mm_lock);
>   	if (ret)
>   		return ret;
> @@ -130,10 +140,17 @@ struct v3d_bo *v3d_bo_create(struct drm_device *dev, struct drm_file *file_priv,
>   			     size_t unaligned_size)
>   {
>   	struct drm_gem_shmem_object *shmem_obj;
> +	struct v3d_dev *v3d = to_v3d_dev(dev);
>   	struct v3d_bo *bo;
>   	int ret;
>   
> -	shmem_obj = drm_gem_shmem_create(dev, unaligned_size);
> +	/* Let the user opt out of allocating the BOs with THP */
> +	if (v3d->gemfs)
> +		shmem_obj = drm_gem_shmem_create_with_mnt(dev, unaligned_size,
> +							  v3d->gemfs);
> +	else
> +		shmem_obj = drm_gem_shmem_create(dev, unaligned_size);
> +
>   	if (IS_ERR(shmem_obj))
>   		return ERR_CAST(shmem_obj);
>   	bo = to_v3d_bo(&shmem_obj->base);