[RFC PATCH 16/18] drm/amdgpu: Implement SET_PRIORITY GEM op

[Christian König]

Am 24.04.24 um 18:57 schrieb Friedrich Vock:
> Used by userspace to adjust buffer priorities in response to changes in
> application demand and memory pressure.

Yeah, that was discussed over and over again. One big design criteria is 
that we can't have global priorities from userspace!

The background here is that this can trivially be abused.

What we can do is to have per process priorities, but that needs to be 
in the VM subsystem.

That's also the reason why I personally think that the handling 
shouldn't be inside TTM at all.

Regards,
Christian.

>
> Signed-off-by: Friedrich Vock <friedrich.vock at gmx.de>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 20 ++++++++++++++++++++
>   include/uapi/drm/amdgpu_drm.h           |  1 +
>   2 files changed, 21 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> index 5ca13e2e50f50..6107810a9c205 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> @@ -836,8 +836,10 @@ int amdgpu_gem_op_ioctl(struct drm_device *dev, void *data,
>   {
>   	struct amdgpu_device *adev = drm_to_adev(dev);
>   	struct drm_amdgpu_gem_op *args = data;
> +	struct ttm_resource_manager *man;
>   	struct drm_gem_object *gobj;
>   	struct amdgpu_vm_bo_base *base;
> +	struct ttm_operation_ctx ctx;
>   	struct amdgpu_bo *robj;
>   	int r;
>
> @@ -851,6 +853,9 @@ int amdgpu_gem_op_ioctl(struct drm_device *dev, void *data,
>   	if (unlikely(r))
>   		goto out;
>
> +	memset(&ctx, 0, sizeof(ctx));
> +	ctx.interruptible = true;
> +
>   	switch (args->op) {
>   	case AMDGPU_GEM_OP_GET_GEM_CREATE_INFO: {
>   		struct drm_amdgpu_gem_create_in info;
> @@ -898,6 +903,21 @@ int amdgpu_gem_op_ioctl(struct drm_device *dev, void *data,
>
>   		amdgpu_bo_unreserve(robj);
>   		break;
> +	case AMDGPU_GEM_OP_SET_PRIORITY:
> +		if (args->value > AMDGPU_BO_PRIORITY_MAX_USER)
> +			args->value = AMDGPU_BO_PRIORITY_MAX_USER;
> +		ttm_bo_update_priority(&robj->tbo, args->value);
> +		if (robj->tbo.evicted_type != TTM_NUM_MEM_TYPES) {
> +			ttm_bo_try_unevict(&robj->tbo, &ctx);
> +			amdgpu_bo_unreserve(robj);
> +		} else {
> +			amdgpu_bo_unreserve(robj);
> +			man = ttm_manager_type(robj->tbo.bdev,
> +				robj->tbo.resource->mem_type);
> +			ttm_mem_unevict_evicted(robj->tbo.bdev, man,
> +						true);
> +		}
> +		break;
>   	default:
>   		amdgpu_bo_unreserve(robj);
>   		r = -EINVAL;
> diff --git a/include/uapi/drm/amdgpu_drm.h b/include/uapi/drm/amdgpu_drm.h
> index bdbe6b262a78d..53552dd489b9b 100644
> --- a/include/uapi/drm/amdgpu_drm.h
> +++ b/include/uapi/drm/amdgpu_drm.h
> @@ -531,6 +531,7 @@ union drm_amdgpu_wait_fences {
>
>   #define AMDGPU_GEM_OP_GET_GEM_CREATE_INFO	0
>   #define AMDGPU_GEM_OP_SET_PLACEMENT		1
> +#define AMDGPU_GEM_OP_SET_PRIORITY              2
>
>   /* Sets or returns a value associated with a buffer. */
>   struct drm_amdgpu_gem_op {
> --
> 2.44.0
>