Re: [PATCH v2 5/6] drm/panfrost: Implement generic DRM object RSS reporting function

[Boris Brezillon]

On Thu, 24 Aug 2023 02:34:48 +0100
Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx> wrote:

> BO's RSS is updated every time new pages are allocated and mapped for the
> object, either in its entirety at creation time for non-heap buffers, or
> else on demand for heap buffers at GPU page fault's IRQ handler.
> 
> Same calculations had to be done for imported PRIME objects, since backing
> storage for it might have already been allocated by the exporting driver.
> 
> Signed-off-by: Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/panfrost/panfrost_gem.c | 22 ++++++++++++++++++++++
>  drivers/gpu/drm/panfrost/panfrost_gem.h |  5 +++++
>  drivers/gpu/drm/panfrost/panfrost_mmu.c | 16 +++++++++++-----
>  3 files changed, 38 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
> index aea16b0e4dda..c6bd1f16a6d4 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
> @@ -206,6 +206,17 @@ static enum drm_gem_object_status panfrost_gem_status(struct drm_gem_object *obj
>  
>  	return res;
>  }
> +
> +size_t panfrost_gem_rss(struct drm_gem_object *obj)
> +{
> +	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
> +
> +	if (!bo->base.pages)
> +		return 0;
> +
> +	return bo->rss_size;
> +}
> +
>  static const struct drm_gem_object_funcs panfrost_gem_funcs = {
>  	.free = panfrost_gem_free_object,
>  	.open = panfrost_gem_open,
> @@ -218,6 +229,7 @@ static const struct drm_gem_object_funcs panfrost_gem_funcs = {
>  	.vunmap = drm_gem_shmem_object_vunmap,
>  	.mmap = drm_gem_shmem_object_mmap,
>  	.status = panfrost_gem_status,
> +	.rss = panfrost_gem_rss,
>  	.vm_ops = &drm_gem_shmem_vm_ops,
>  };
>  
> @@ -274,13 +286,23 @@ panfrost_gem_prime_import_sg_table(struct drm_device *dev,
>  {
>  	struct drm_gem_object *obj;
>  	struct panfrost_gem_object *bo;
> +	struct scatterlist *sgl;
> +	unsigned int count;
> +	size_t total = 0;
>  
>  	obj = drm_gem_shmem_prime_import_sg_table(dev, attach, sgt);
>  	if (IS_ERR(obj))
>  		return ERR_CAST(obj);
>  
> +	for_each_sgtable_dma_sg(sgt, sgl, count) {
> +		size_t len = sg_dma_len(sgl);
> +
> +		total += len;
> +	}

Why not simply have bo->rss_size = obj->size here? Not sure I see a
reason to not trust dma_buf?

> +
>  	bo = to_panfrost_bo(obj);
>  	bo->noexec = true;
> +	bo->rss_size = total;
>  
>  	return obj;
>  }
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
> index e06f7ceb8f73..e2a7c46403c7 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
> @@ -36,6 +36,11 @@ struct panfrost_gem_object {
>  	 */
>  	atomic_t gpu_usecount;
>  
> +	/*
> +	 * Object chunk size currently mapped onto physical memory
> +	 */
> +	size_t rss_size;
> +
>  	bool noexec		:1;
>  	bool is_heap		:1;
>  	bool is_purgable	:1;
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index c0123d09f699..e03a5a9da06f 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> @@ -285,17 +285,19 @@ static void panfrost_mmu_flush_range(struct panfrost_device *pfdev,
>  	pm_runtime_put_autosuspend(pfdev->dev);
>  }
>  
> -static int mmu_map_sg(struct panfrost_device *pfdev, struct panfrost_mmu *mmu,
> +static size_t mmu_map_sg(struct panfrost_device *pfdev, struct panfrost_mmu *mmu,
>  		      u64 iova, int prot, struct sg_table *sgt)
>  {
>  	unsigned int count;
>  	struct scatterlist *sgl;
>  	struct io_pgtable_ops *ops = mmu->pgtbl_ops;
>  	u64 start_iova = iova;
> +	size_t total = 0;
>  
>  	for_each_sgtable_dma_sg(sgt, sgl, count) {
>  		unsigned long paddr = sg_dma_address(sgl);
>  		size_t len = sg_dma_len(sgl);
> +		total += len;
>  
>  		dev_dbg(pfdev->dev, "map: as=%d, iova=%llx, paddr=%lx, len=%zx", mmu->as, iova, paddr, len);
>  
> @@ -315,7 +317,7 @@ static int mmu_map_sg(struct panfrost_device *pfdev, struct panfrost_mmu *mmu,
>  
>  	panfrost_mmu_flush_range(pfdev, mmu, start_iova, iova - start_iova);
>  
> -	return 0;
> +	return total;
>  }
>  
>  int panfrost_mmu_map(struct panfrost_gem_mapping *mapping)
> @@ -326,6 +328,7 @@ int panfrost_mmu_map(struct panfrost_gem_mapping *mapping)
>  	struct panfrost_device *pfdev = to_panfrost_device(obj->dev);
>  	struct sg_table *sgt;
>  	int prot = IOMMU_READ | IOMMU_WRITE;
> +	size_t mapped_size;
>  
>  	if (WARN_ON(mapping->active))
>  		return 0;
> @@ -337,9 +340,10 @@ int panfrost_mmu_map(struct panfrost_gem_mapping *mapping)
>  	if (WARN_ON(IS_ERR(sgt)))
>  		return PTR_ERR(sgt);
>  
> -	mmu_map_sg(pfdev, mapping->mmu, mapping->mmnode.start << PAGE_SHIFT,
> +	mapped_size = mmu_map_sg(pfdev, mapping->mmu, mapping->mmnode.start << PAGE_SHIFT,
>  		   prot, sgt);
>  	mapping->active = true;
> +	bo->rss_size += mapped_size;

Actually, the GEM might be resident even before panfrost_mmu_map() is
called: as soon as drm_gem_shmem_get_pages[_locked]() is called, it's
resident (might get evicted after that point though). That means any
mmap coming from userspace will make the buffer resident too. I know
we're automatically mapping GEMs to the GPU VM in panfrost_gem_open(),
so it makes no difference, but I think I'd prefer if we keep ->rss_size
for heap BOs only (we probably want to rename it heap_rss_size) and
then have


	if (bo->is_heap)
		return bo->heap_rss_size;
	else if (bo->base.pages)
		return bo->base.base.size;
	else
		return 0;

in panfrost_gem_rss().

>  
>  	return 0;
>  }
> @@ -447,6 +451,7 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
>  	pgoff_t page_offset;
>  	struct sg_table *sgt;
>  	struct page **pages;
> +	size_t mapped_size;
>  
>  	bomapping = addr_to_mapping(pfdev, as, addr);
>  	if (!bomapping)
> @@ -518,10 +523,11 @@ static int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as,
>  	if (ret)
>  		goto err_map;
>  
> -	mmu_map_sg(pfdev, bomapping->mmu, addr,
> -		   IOMMU_WRITE | IOMMU_READ | IOMMU_NOEXEC, sgt);
> +	mapped_size = mmu_map_sg(pfdev, bomapping->mmu, addr,
> +				 IOMMU_WRITE | IOMMU_READ | IOMMU_NOEXEC, sgt);
>  
>  	bomapping->active = true;
> +	bo->rss_size += mapped_size;
>  
>  	dev_dbg(pfdev->dev, "mapped page fault @ AS%d %llx", as, addr);
>