Re: [PATCH 11/11] drm/i915: Move active to vma

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Jul 08, 2013 at 11:08:42PM -0700, Ben Widawsky wrote:
> Probably need to squash whole thing, or just the inactive part, tbd...
> 
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>

I agree that we need vma->active, but I'm not sold on removing
obj->active. Atm we have to use-cases for checking obj->active:
- In the evict/unbind code to check whether the gpu is still using this
  specific mapping. This use-case nicely fits into checking vma->active.
- In the shrinker code and everywhere we want to do cpu access we only
  care about whether the gpu is accessing the object, not at all through
  which mapping precisely. There a vma-independant obj->active sounds much
  saner.

Note though that just keeping track of vma->active isn't too useful, since
if some other vma is keeping the object busy we'll still stall on that one
for eviction. So we'd need a vma->ring and vma->last_rendering_seqno, too.

At that point I wonder a bit whether all this complexity is worth it ...

I need to ponder this some more.
-Daniel

> ---
>  drivers/gpu/drm/i915/i915_drv.h | 14 ++++++------
>  drivers/gpu/drm/i915/i915_gem.c | 47 ++++++++++++++++++++++++-----------------
>  2 files changed, 35 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 38d07f2..e6694ae 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -541,6 +541,13 @@ struct i915_vma {
>  	struct drm_i915_gem_object *obj;
>  	struct i915_address_space *vm;
>  
> +	/**
> +	 * This is set if the object is on the active lists (has pending
> +	 * rendering and so a non-zero seqno), and is not set if it i s on
> +	 * inactive (ready to be unbound) list.
> +	 */
> +	unsigned int active:1;
> +
>  	/** This object's place on the active/inactive lists */
>  	struct list_head mm_list;
>  
> @@ -1250,13 +1257,6 @@ struct drm_i915_gem_object {
>  	struct list_head exec_list;
>  
>  	/**
> -	 * This is set if the object is on the active lists (has pending
> -	 * rendering and so a non-zero seqno), and is not set if it i s on
> -	 * inactive (ready to be unbound) list.
> -	 */
> -	unsigned int active:1;
> -
> -	/**
>  	 * This is set if the object has been written to since last bound
>  	 * to the GTT
>  	 */
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index c2ecb78..b87073b 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -137,7 +137,13 @@ int i915_mutex_lock_interruptible(struct drm_device *dev)
>  /* NB: Not the same as !i915_gem_object_is_inactive */
>  bool i915_gem_object_is_active(struct drm_i915_gem_object *obj)
>  {
> -	return obj->active;
> +	struct i915_vma *vma;
> +
> +	list_for_each_entry(vma, &obj->vma_list, vma_link)
> +		if (vma->active)
> +			return true;
> +
> +	return false;
>  }
>  
>  static inline bool
> @@ -1899,14 +1905,14 @@ i915_gem_object_move_to_active(struct drm_i915_gem_object *obj,
>  	BUG_ON(ring == NULL);
>  	obj->ring = ring;
>  
> +	/* Move from whatever list we were on to the tail of execution. */
> +	vma = i915_gem_obj_to_vma(obj, vm);
>  	/* Add a reference if we're newly entering the active list. */
> -	if (!i915_gem_object_is_active(obj)) {
> +	if (!vma->active) {
>  		drm_gem_object_reference(&obj->base);
> -		obj->active = 1;
> +		vma->active = 1;
>  	}
>  
> -	/* Move from whatever list we were on to the tail of execution. */
> -	vma = i915_gem_obj_to_vma(obj, vm);
>  	list_move_tail(&vma->mm_list, &vm->active_list);
>  	list_move_tail(&obj->ring_list, &ring->active_list);
>  
> @@ -1927,16 +1933,23 @@ i915_gem_object_move_to_active(struct drm_i915_gem_object *obj,
>  }
>  
>  static void
> -i915_gem_object_move_to_inactive(struct drm_i915_gem_object *obj,
> -				 struct i915_address_space *vm)
> +i915_gem_object_move_to_inactive(struct drm_i915_gem_object *obj)
>  {
> +	struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
> +	struct i915_address_space *vm;
>  	struct i915_vma *vma;
> +	int i = 0;
>  
>  	BUG_ON(obj->base.write_domain & ~I915_GEM_GPU_DOMAINS);
> -	BUG_ON(!i915_gem_object_is_active(obj));
>  
> -	vma = i915_gem_obj_to_vma(obj, vm);
> -	list_move_tail(&vma->mm_list, &vm->inactive_list);
> +	list_for_each_entry(vm, &dev_priv->vm_list, global_link) {
> +		vma = i915_gem_obj_to_vma(obj, vm);
For paranoia we might want to track the vm used to run a batch in it
request struct, then we

> +		if (!vma || !vma->active)
> +			continue;
> +		list_move_tail(&vma->mm_list, &vm->inactive_list);
> +		vma->active = 0;
> +		i++;
> +	}
>  
>  	list_del_init(&obj->ring_list);
>  	obj->ring = NULL;
> @@ -1948,8 +1961,8 @@ i915_gem_object_move_to_inactive(struct drm_i915_gem_object *obj,
>  	obj->last_fenced_seqno = 0;
>  	obj->fenced_gpu_access = false;
>  
> -	obj->active = 0;
> -	drm_gem_object_unreference(&obj->base);
> +	while (i--)
> +		drm_gem_object_unreference(&obj->base);
>  
>  	WARN_ON(i915_verify_lists(dev));
>  }
> @@ -2272,15 +2285,13 @@ static void i915_gem_reset_ring_lists(struct drm_i915_private *dev_priv,
>  	}
>  
>  	while (!list_empty(&ring->active_list)) {
> -		struct i915_address_space *vm;
>  		struct drm_i915_gem_object *obj;
>  
>  		obj = list_first_entry(&ring->active_list,
>  				       struct drm_i915_gem_object,
>  				       ring_list);
>  
> -		list_for_each_entry(vm, &dev_priv->vm_list, global_link)
> -			i915_gem_object_move_to_inactive(obj, vm);
> +		i915_gem_object_move_to_inactive(obj);
>  	}
>  }
>  
> @@ -2356,8 +2367,6 @@ i915_gem_retire_requests_ring(struct intel_ring_buffer *ring)
>  	 * by the ringbuffer to the flushing/inactive lists as appropriate.
>  	 */
>  	while (!list_empty(&ring->active_list)) {
> -		struct drm_i915_private *dev_priv = ring->dev->dev_private;
> -		struct i915_address_space *vm;
>  		struct drm_i915_gem_object *obj;
>  
>  		obj = list_first_entry(&ring->active_list,
> @@ -2367,8 +2376,8 @@ i915_gem_retire_requests_ring(struct intel_ring_buffer *ring)
>  		if (!i915_seqno_passed(seqno, obj->last_read_seqno))
>  			break;
>  
> -		list_for_each_entry(vm, &dev_priv->vm_list, global_link)
> -			i915_gem_object_move_to_inactive(obj, vm);
> +		BUG_ON(!i915_gem_object_is_active(obj));
> +		i915_gem_object_move_to_inactive(obj);
>  	}
>  
>  	if (unlikely(ring->trace_irq_seqno &&
> -- 
> 1.8.3.2
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch