Re: [PATCH v3 7/8] drm/panfrost: Implement generic DRM object RSS reporting function

Boris Brezillon
2023-09-06T08:01:39Z

On Tue, 5 Sep 2023 19:45:23 +0100
Adrián Larumbe <adrian.larumbe@collabora.com> wrote:

> BO's RSS is updated every time new pages are allocated on demand and mapped
> for the object at GPU page fault's IRQ handler, but only for heap buffers.
> The reason this is unnecessary for non-heap buffers is that they are mapped
> onto the GPU's VA space and backed by physical memory in their entirety at
> BO creation time.
>
> This calculation is unnecessary for imported PRIME objects, since heap
> buffers cannot be exported by our driver, and the actual BO RSS size is the
> one reported in its attached dmabuf structure.
>
> Signed-off-by: Adrián Larumbe <adrian.larumbe@collabora.com>
> ---
> drivers/gpu/drm/panfrost/panfrost_gem.c | 14 ++++++++++++++
> drivers/gpu/drm/panfrost/panfrost_gem.h | 5 +++++
> drivers/gpu/drm/panfrost/panfrost_mmu.c | 12 ++++++++----
> 3 files changed, 27 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
> index 7d8f83d20539..cb92c0ed7615 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
> @@ -208,6 +208,19 @@ static enum drm_gem_object_status panfrost_gem_status(struct drm_gem_object *obj
> return res;
> }
>
> +static size_t panfrost_gem_rss(struct drm_gem_object *obj)
> +{
> + struct panfrost_gem_object *bo = to_panfrost_bo(obj);
> +
> + if (bo->is_heap)
> + return bo->heap_rss_size;
> + else if (bo->base.pages) {
> + WARN_ON(bo->heap_rss_size);
> + return bo->base.base.size;
> + } else
> + return 0;

Nit: please add brackets on all conditional blocks, even if only the
second one needs it.

> +}
> +
> static const struct drm_gem_object_funcs panfrost_gem_funcs = {
> .free = panfrost_gem_free_object,
> .open = panfrost_gem_open,
> @@ -220,6 +233,7 @@ 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,
> };
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.h b/drivers/gpu/drm/panfrost/panfrost_gem.h
> index ad2877eeeccd..13c0a8149c3a 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 heap_rss_size;
> +
> bool noexec :1;
> bool is_heap :1;
> };
> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> index d54d4e7b2195..67c206124781 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)
> @@ -447,6 +449,7 @@ 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 +521,11 @@ 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->heap_rss_size += mapped_size;

The alloc-on-fault granularity is set static (2MB), so no need to
make mmu_map_sg() return the mapped size, we can just do += SZ_2M if
things worked.

>
> dev_dbg(pfdev->dev, "mapped page fault @ AS%d %llx", as, addr);
>