On Thu, 24 Aug 2023 02:34:46 +0100
Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx> wrote:
> A new DRM GEM object function is added so that drm_show_memory_stats can
> provider more accurate memory usage numbers.
s/provider/provide/
>
> Ideally, in panfrost_gem_status, the BO's purgeable flag would be checked
> after locking the driver's shrinker mutex, but drm_show_memory_stats takes
> over the drm file's object handle database spinlock, so there's potential
> for a race condition here.
Yeah, I don't think it matters much if we report a BO non-purgeable,
and this BO becomes purgeable in the meantime. You'd have the same
problem
>
> Signed-off-by: Adrián Larumbe <adrian.larumbe@xxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/panfrost/panfrost_drv.c | 9 +++++++--
> drivers/gpu/drm/panfrost/panfrost_gem.c | 12 ++++++++++++
> drivers/gpu/drm/panfrost/panfrost_gem.h | 1 +
> 3 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_drv.c b/drivers/gpu/drm/panfrost/panfrost_drv.c
> index 3fd372301019..93d5f5538c0b 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_drv.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_drv.c
> @@ -440,11 +440,14 @@ static int panfrost_ioctl_madvise(struct drm_device *dev, void *data,
> args->retained = drm_gem_shmem_madvise(&bo->base, args->madv);
>
> if (args->retained) {
> - if (args->madv == PANFROST_MADV_DONTNEED)
> + if (args->madv == PANFROST_MADV_DONTNEED) {
> list_move_tail(&bo->base.madv_list,
> &pfdev->shrinker_list);
> - else if (args->madv == PANFROST_MADV_WILLNEED)
> + bo->is_purgable = true;
> + } else if (args->madv == PANFROST_MADV_WILLNEED) {
> list_del_init(&bo->base.madv_list);
> + bo->is_purgable = false;
Should we really flag the BO as purgeable if it's already been evicted
(args->retained == false)?
> + }
> }
>
> out_unlock_mappings:
> @@ -559,6 +562,8 @@ static void panfrost_show_fdinfo(struct drm_printer *p, struct drm_file *file)
> struct panfrost_device *pfdev = dev->dev_private;
>
> panfrost_gpu_show_fdinfo(pfdev, file->driver_priv, p);
> +
> + drm_show_memory_stats(p, file);
> }
>
> static const struct file_operations panfrost_drm_driver_fops = {
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
> index 3c812fbd126f..aea16b0e4dda 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
> @@ -195,6 +195,17 @@ static int panfrost_gem_pin(struct drm_gem_object *obj)
> return drm_gem_shmem_pin(&bo->base);
> }
>
> +static enum drm_gem_object_status panfrost_gem_status(struct drm_gem_object *obj)
> +{
> + struct panfrost_gem_object *bo = to_panfrost_bo(obj);
> + enum drm_gem_object_status res = 0;
> +
> + res |= (bo->is_purgable) ? DRM_GEM_OBJECT_PURGEABLE : 0;
Why not checking bo->base.madv here instead of adding an is_purgeable
field?
> +
> + res |= (bo->base.pages) ? DRM_GEM_OBJECT_RESIDENT : 0;
Does it make sense to have DRM_GEM_OBJECT_PURGEABLE set when
DRM_GEM_OBJECT_RESIDENT is not?
> +
> + return res;
> +}
> static const struct drm_gem_object_funcs panfrost_gem_funcs = {
> .free = panfrost_gem_free_object,
> .open = panfrost_gem_open,
> @@ -206,6 +217,7 @@ static const struct drm_gem_object_funcs panfrost_gem_funcs = {
> .vmap = drm_gem_shmem_object_vmap,
> .vunmap = drm_gem_shmem_object_vunmap,
> .mmap = drm_gem_shmem_object_mmap,
> + .status = panfrost_gem_status,
> .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..e06f7ceb8f73 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gem.h
> +++ b/drivers/gpu/drm/panfrost/panfrost_gem.h
> @@ -38,6 +38,7 @@ struct panfrost_gem_object {
>
> bool noexec :1;
> bool is_heap :1;
> + bool is_purgable :1;
> };
>
> struct panfrost_gem_mapping {
