[PATCH v8 4/5] drm/drm_file: Add DRM obj's RSS reporting function for fdinfo

[Rob Clark]

On Fri, Sep 29, 2023 at 11:16 AM Adrián Larumbe
<adrian.larumbe at collabora.com> 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 and purgeable sizes for their BOs.
>
> Signed-off-by: Adrián Larumbe <adrian.larumbe at collabora.com>
> Reviewed-by: Boris Brezillon <boris.brezillon at collabora.com>
> Reviewed-by: Steven Price <steven.price at arm.com>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>

Reviewed-by: Rob Clark <robdclark at gmail.com>

> ---
>  drivers/gpu/drm/drm_file.c | 8 +++++---
>  include/drm/drm_gem.h      | 9 +++++++++
>  2 files changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
> index 883d83bc0e3d..9a1bd8d0d785 100644
> --- a/drivers/gpu/drm/drm_file.c
> +++ b/drivers/gpu/drm/drm_file.c
> @@ -930,6 +930,8 @@ void drm_show_memory_stats(struct drm_printer *p, struct drm_file *file)
>         spin_lock(&file->table_lock);
>         idr_for_each_entry (&file->object_idr, obj, id) {
>                 enum drm_gem_object_status s = 0;
> +               size_t add_size = (obj->funcs && obj->funcs->rss) ?
> +                       obj->funcs->rss(obj) : obj->size;
>
>                 if (obj->funcs && obj->funcs->status) {
>                         s = obj->funcs->status(obj);
> @@ -944,7 +946,7 @@ void drm_show_memory_stats(struct drm_printer *p, struct drm_file *file)
>                 }
>
>                 if (s & DRM_GEM_OBJECT_RESIDENT) {
> -                       status.resident += obj->size;
> +                       status.resident += add_size;
>                 } else {
>                         /* If already purged or not yet backed by pages, don't
>                          * count it as purgeable:
> @@ -953,14 +955,14 @@ void drm_show_memory_stats(struct drm_printer *p, struct drm_file *file)
>                 }
>
>                 if (!dma_resv_test_signaled(obj->resv, dma_resv_usage_rw(true))) {
> -                       status.active += obj->size;
> +                       status.active += add_size;
>
>                         /* If still active, don't count as purgeable: */
>                         s &= ~DRM_GEM_OBJECT_PURGEABLE;
>                 }
>
>                 if (s & DRM_GEM_OBJECT_PURGEABLE)
> -                       status.purgeable += obj->size;
> +                       status.purgeable += add_size;
>         }
>         spin_unlock(&file->table_lock);
>
> diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
> index bc9f6aa2f3fe..16364487fde9 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:
>          *
> --
> 2.42.0
>