On Thu, 24 Aug 2023 02:34:47 +0100
Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx> wrote:
> Some BO's might be mapped onto physical memory chunkwise and on demand,
> like Panfrost's tiler heap. In this case, even though the
> drm_gem_shmem_object page array might already be allocated, only a very
> small fraction of the BO is currently backed by system memory, but
> drm_show_memory_stats will then proceed to add its entire virtual size to
> the file's total resident size regardless.
>
> This led to very unrealistic RSS sizes being reckoned for Panfrost, where
> said tiler heap buffer is initially allocated with a virtual size of 128
> MiB, but only a small part of it will eventually be backed by system memory
> after successive GPU page faults.
>
> Provide a new DRM object generic function that would allow drivers to
> return a more accurate RSS size for their BOs.
>
> Signed-off-by: Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx>
Reviewed-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_file.c | 5 ++++-
> include/drm/drm_gem.h | 9 +++++++++
> 2 files changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> index 883d83bc0e3d..762965e3d503 100644
> --- a/drivers/gpu/drm/drm_file.c
> +++ b/drivers/gpu/drm/drm_file.c
> @@ -944,7 +944,10 @@ void drm_show_memory_stats(struct drm_printer *p, struct drm_file *file)
> }
>
> if (s & DRM_GEM_OBJECT_RESIDENT) {
> - status.resident += obj->size;
> + if (obj->funcs && obj->funcs->rss)
> + status.resident += obj->funcs->rss(obj);
> + else
> + status.resident += obj->size;
> } else {
> /* If already purged or not yet backed by pages, don't
> * count it as purgeable:
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index c0b13c43b459..78ed9fab6044 100644
> --- a/include/drm/drm_gem.h
> +++ b/include/drm/drm_gem.h
> @@ -208,6 +208,15 @@ struct drm_gem_object_funcs {
> */
> enum drm_gem_object_status (*status)(struct drm_gem_object *obj);
>
> + /**
> + * @rss:
> + *
> + * Return resident size of the object in physical memory.
> + *
> + * Called by drm_show_memory_stats().
> + */
> + size_t (*rss)(struct drm_gem_object *obj);
> +
> /**
> * @vm_ops:
> *
