On Thu, May 26, 2016 at 10:34:57AM +0100, Chris Wilson wrote:
> Currently the plane's index is determined by walking the list of all
> planes in the mode and finding the position of that plane in the list. A
> linear walk, especially a linear walk within a linear walk as frequently
> conceived by i915.ko [O(N^2)] quickly comes to dominate profiles.
>
> The plane's index is constant for as long as no earlier planes are
> removed from the list. For most drivers, planes are static, determined
> at boot and then untouched until shutdown. Storing the index upon
> construction and then only walking the tail upon removal should
> be a major improvement for all.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Cc: Matt Roper <matthew.d.roper@xxxxxxxxx>
I've been wondering about the cost of these silly walks myself.
Patch looks sane to me
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Same for crtcs?
> ---
> drivers/gpu/drm/drm_crtc.c | 38 +++++++++-----------------------------
> include/drm/drm_crtc.h | 6 +++++-
> 2 files changed, 14 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 3a0384cce4a2..00ee01126b6f 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -1302,7 +1302,7 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
> plane->type = type;
>
> list_add_tail(&plane->head, &config->plane_list);
> - config->num_total_plane++;
> + plane->index = config->num_total_plane++;
> if (plane->type == DRM_PLANE_TYPE_OVERLAY)
> config->num_overlay_plane++;
>
> @@ -1369,6 +1369,7 @@ EXPORT_SYMBOL(drm_plane_init);
> void drm_plane_cleanup(struct drm_plane *plane)
> {
> struct drm_device *dev = plane->dev;
> + struct drm_plane *other;
>
> drm_modeset_lock_all(dev);
> kfree(plane->format_types);
> @@ -1376,6 +1377,10 @@ void drm_plane_cleanup(struct drm_plane *plane)
>
> BUG_ON(list_empty(&plane->head));
>
> + other = list_next_entry(plane, head);
> + list_for_each_entry_from(other, &dev->mode_config.plane_list, head)
> + other->index--;
> +
> list_del(&plane->head);
> dev->mode_config.num_total_plane--;
> if (plane->type == DRM_PLANE_TYPE_OVERLAY)
> @@ -1393,29 +1398,6 @@ void drm_plane_cleanup(struct drm_plane *plane)
> EXPORT_SYMBOL(drm_plane_cleanup);
>
> /**
> - * drm_plane_index - find the index of a registered plane
> - * @plane: plane to find index for
> - *
> - * Given a registered plane, return the index of that CRTC within a DRM
> - * device's list of planes.
> - */
> -unsigned int drm_plane_index(struct drm_plane *plane)
> -{
> - unsigned int index = 0;
> - struct drm_plane *tmp;
> -
> - drm_for_each_plane(tmp, plane->dev) {
> - if (tmp == plane)
> - return index;
> -
> - index++;
> - }
> -
> - BUG();
> -}
> -EXPORT_SYMBOL(drm_plane_index);
> -
> -/**
> * drm_plane_from_index - find the registered plane at an index
> * @dev: DRM device
> * @idx: index of registered plane to find for
> @@ -1427,13 +1409,11 @@ struct drm_plane *
> drm_plane_from_index(struct drm_device *dev, int idx)
> {
> struct drm_plane *plane;
> - unsigned int i = 0;
>
> - drm_for_each_plane(plane, dev) {
> - if (i == idx)
> + drm_for_each_plane(plane, dev)
> + if (idx == plane->index)
> return plane;
> - i++;
> - }
> +
> return NULL;
> }
> EXPORT_SYMBOL(drm_plane_from_index);
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 9771428e1ba8..eda3b1b3d3b4 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -1543,6 +1543,7 @@ struct drm_plane {
> struct drm_object_properties properties;
>
> enum drm_plane_type type;
> + unsigned index;
>
> const struct drm_plane_helper_funcs *helper_private;
>
> @@ -2316,7 +2317,10 @@ extern int drm_plane_init(struct drm_device *dev,
> const uint32_t *formats, unsigned int format_count,
> bool is_primary);
> extern void drm_plane_cleanup(struct drm_plane *plane);
> -extern unsigned int drm_plane_index(struct drm_plane *plane);
> +static inline unsigned int drm_plane_index(struct drm_plane *plane)
> +{
> + return plane->index;
> +}
> extern struct drm_plane * drm_plane_from_index(struct drm_device *dev, int idx);
> extern void drm_plane_force_disable(struct drm_plane *plane);
> extern int drm_plane_check_pixel_format(const struct drm_plane *plane,
> --
> 2.8.1
>
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--
Ville Syrjälä
Intel OTC
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