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

Adrián Larumbe
2023-09-09T16:42:53Z

On 06.09.2023 10:01, Boris Brezillon wrote:
>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.

At the moment mmu_map_sg is treated as though it always succeeds in mapping the
page. Would it be alright if I changed it so that we take into account the
unlikely case that ops->map_pages might fail?
Something like this: https://gitlab.collabora.com/-/snippets/323

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