Hi Dmitry,
Sorry for chiming in only now :-/.
On Tue, 14 Mar 2023 05:26:52 +0300
Dmitry Osipenko <dmitry.osipe...@collabora.com> wrote:
> And new pages_pin_count field to struct drm_gem_shmem_object that will
> determine whether pages are evictable by memory shrinker. The pages will
> be evictable only when pages_pin_count=0. This patch prepares code for
> addition of the memory shrinker that will utilize the new field.
>
> Signed-off-by: Dmitry Osipenko <dmitry.osipe...@collabora.com>
> ---
> drivers/gpu/drm/drm_gem_shmem_helper.c | 7 +++++++
> include/drm/drm_gem_shmem_helper.h | 9 +++++++++
> 2 files changed, 16 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
> b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 4da9c9c39b9a..81d61791f874 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -277,6 +277,8 @@ static int drm_gem_shmem_pin_locked(struct
> drm_gem_shmem_object *shmem)
> drm_WARN_ON(obj->dev, obj->import_attach);
>
> ret = drm_gem_shmem_get_pages(shmem);
> + if (!ret)
> + shmem->pages_pin_count++;
>
> return ret;
> }
> @@ -289,7 +291,12 @@ static void drm_gem_shmem_unpin_locked(struct
> drm_gem_shmem_object *shmem)
>
> drm_WARN_ON(obj->dev, obj->import_attach);
>
> + if (drm_WARN_ON_ONCE(obj->dev, !shmem->pages_pin_count))
> + return;
> +
> drm_gem_shmem_put_pages(shmem);
> +
> + shmem->pages_pin_count--;
> }
>
> /**
> diff --git a/include/drm/drm_gem_shmem_helper.h
> b/include/drm/drm_gem_shmem_helper.h
> index 20ddcd799df9..7d823c9fc480 100644
> --- a/include/drm/drm_gem_shmem_helper.h
> +++ b/include/drm/drm_gem_shmem_helper.h
> @@ -39,6 +39,15 @@ struct drm_gem_shmem_object {
> */
> unsigned int pages_use_count;
>
> + /**
> + * @pages_pin_count:
> + *
> + * Reference count on the pinned pages table.
> + * The pages allowed to be evicted by memory shrinker
> + * only when the count is zero.
> + */
> + unsigned int pages_pin_count;
s/pages_pin_count/pin_count/ ?
And do we really need both pages_pin_count and pages_use_count. Looks
like they both serve the same purpose, with one exception:
pages_use_count is also incremented in the get_pages_sgt_locked() path,
but you probably don't want it to prevent GEM eviction. Assuming
your goal with this pin_count field is to check if a GEM object is
evictable, it can be done with something like
bool
drm_gem_shmem_is_evictable_locked(struct drm_gem_shmem_object *shmem)
{
dma_resv_assert_held(shmem->base.resv);
return shmem->pages_use_count == (shmem->sgt ? 1 : 0);
}
I mean, I'm not against renaming pages_use_count into pin_count, but,
unless I'm missing something, I don't see a good reason to keep both.
Regards,
Boris
