[RFC v4 4/8] dmabuf: heaps: export system_heap buffers with GPU cgroup charging

[Daniel Vetter]

On Mon, Mar 28, 2022 at 03:59:43AM +0000, T.J. Mercier wrote:
> From: Hridya Valsaraju <hridya at google.com>
> 
> All DMA heaps now register a new GPU cgroup device upon creation, and the
> system_heap now exports buffers associated with its GPU cgroup device for
> tracking purposes.
> 
> Signed-off-by: Hridya Valsaraju <hridya at google.com>
> Signed-off-by: T.J. Mercier <tjmercier at google.com>
> 
> ---
> v3 changes
> Use more common dual author commit message format per John Stultz.
> 
> v2 changes
> Move dma-buf cgroup charge transfer from a dma_buf_op defined by every
> heap to a single dma-buf function for all heaps per Daniel Vetter and
> Christian König.

Apologies for being out of the loop quite a bit. I scrolled through this
all and I think it looks good to get going.

The only thing I have is whether we should move the cgroup controllers out
of dma-buf heaps, since that's rather android centric. E.g.
- a system gpucg_device which is used by all the various single page
  allocators (dma-buf heap but also shmem helpers and really anything
  else)
- same for cma, again both for dma-buf heaps and also for the gem cma
  helpers in drm

Otherwise this will only work on non-upstream android where gpu drivers
allocate everything from dma-buf heap. If you use something like the x86
android project with mesa drivers, then driver-internal buffers will be
allocated through gem and not through dma-buf heaps. Or at least I think
that's how it works.

But also meh, we can fix this fairly easily later on by adding these
standard gpucg_dev somwehere with a bit of kerneldoc.

Anyway has my all my ack, but don't count this as my in-depth review :-)
-Daniel

> ---
>  drivers/dma-buf/dma-heap.c          | 27 +++++++++++++++++++++++++++
>  drivers/dma-buf/heaps/system_heap.c |  3 +++
>  include/linux/dma-heap.h            | 11 +++++++++++
>  3 files changed, 41 insertions(+)
> 
> diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
> index 8f5848aa144f..885072427775 100644
> --- a/drivers/dma-buf/dma-heap.c
> +++ b/drivers/dma-buf/dma-heap.c
> @@ -7,6 +7,7 @@
>   */
>  
>  #include <linux/cdev.h>
> +#include <linux/cgroup_gpu.h>
>  #include <linux/debugfs.h>
>  #include <linux/device.h>
>  #include <linux/dma-buf.h>
> @@ -31,6 +32,7 @@
>   * @heap_devt		heap device node
>   * @list		list head connecting to list of heaps
>   * @heap_cdev		heap char device
> + * @gpucg_dev		gpu cgroup device for memory accounting
>   *
>   * Represents a heap of memory from which buffers can be made.
>   */
> @@ -41,6 +43,9 @@ struct dma_heap {
>  	dev_t heap_devt;
>  	struct list_head list;
>  	struct cdev heap_cdev;
> +#ifdef CONFIG_CGROUP_GPU
> +	struct gpucg_device gpucg_dev;
> +#endif
>  };
>  
>  static LIST_HEAD(heap_list);
> @@ -216,6 +221,26 @@ const char *dma_heap_get_name(struct dma_heap *heap)
>  	return heap->name;
>  }
>  
> +#ifdef CONFIG_CGROUP_GPU
> +/**
> + * dma_heap_get_gpucg_dev() - get struct gpucg_device for the heap.
> + * @heap: DMA-Heap to get the gpucg_device struct for.
> + *
> + * Returns:
> + * The gpucg_device struct for the heap. NULL if the GPU cgroup controller is
> + * not enabled.
> + */
> +struct gpucg_device *dma_heap_get_gpucg_dev(struct dma_heap *heap)
> +{
> +	return &heap->gpucg_dev;
> +}
> +#else /* CONFIG_CGROUP_GPU */
> +struct gpucg_device *dma_heap_get_gpucg_dev(struct dma_heap *heap)
> +{
> +	return NULL;
> +}
> +#endif /* CONFIG_CGROUP_GPU */
> +
>  struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
>  {
>  	struct dma_heap *heap, *h, *err_ret;
> @@ -288,6 +313,8 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
>  	list_add(&heap->list, &heap_list);
>  	mutex_unlock(&heap_list_lock);
>  
> +	gpucg_register_device(dma_heap_get_gpucg_dev(heap), exp_info->name);
> +
>  	return heap;
>  
>  err2:
> diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> index ab7fd896d2c4..752a05c3cfe2 100644
> --- a/drivers/dma-buf/heaps/system_heap.c
> +++ b/drivers/dma-buf/heaps/system_heap.c
> @@ -395,6 +395,9 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap,
>  	exp_info.ops = &system_heap_buf_ops;
>  	exp_info.size = buffer->len;
>  	exp_info.flags = fd_flags;
> +#ifdef CONFIG_CGROUP_GPU
> +	exp_info.gpucg_dev = dma_heap_get_gpucg_dev(heap);
> +#endif
>  	exp_info.priv = buffer;
>  	dmabuf = dma_buf_export(&exp_info);
>  	if (IS_ERR(dmabuf)) {
> diff --git a/include/linux/dma-heap.h b/include/linux/dma-heap.h
> index 0c05561cad6e..e447a61d054e 100644
> --- a/include/linux/dma-heap.h
> +++ b/include/linux/dma-heap.h
> @@ -10,6 +10,7 @@
>  #define _DMA_HEAPS_H
>  
>  #include <linux/cdev.h>
> +#include <linux/cgroup_gpu.h>
>  #include <linux/types.h>
>  
>  struct dma_heap;
> @@ -59,6 +60,16 @@ void *dma_heap_get_drvdata(struct dma_heap *heap);
>   */
>  const char *dma_heap_get_name(struct dma_heap *heap);
>  
> +/**
> + * dma_heap_get_gpucg_dev() - get a pointer to the struct gpucg_device for the
> + * heap.
> + * @heap: DMA-Heap to retrieve gpucg_device for.
> + *
> + * Returns:
> + * The gpucg_device struct for the heap.
> + */
> +struct gpucg_device *dma_heap_get_gpucg_dev(struct dma_heap *heap);
> +
>  /**
>   * dma_heap_add - adds a heap to dmabuf heaps
>   * @exp_info:		information needed to register this heap
> -- 
> 2.35.1.1021.g381101b075-goog
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch