Commit 2236439b authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

drm/vram: Implement lazy unmapping for GEM VRAM buffers 



Frequent mapping and unmapping a buffer object adds overhead for
modifying the page table and creates debug output. Unmapping a buffer
is only required when the memory manager evicts the buffer from its
current location.

v4:
	* WARN_ON if buffer is still mapped during BO cleanup

Signed-off-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: default avatarGerd Hoffmann <kraxel@redhat.com>
Acked-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Reported-and-tested-by: default avatarDavidlohr Bueso <dbueso@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20190906122056.32018-5-tzimmermann@suse.de
parent f3309105

drivers/gpu/drm/drm_gem_vram_helper.c

+41 −8
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ static void drm_gem_vram_cleanup(struct drm_gem_vram_object *gbo) 
	 */



	WARN_ON(gbo->kmap_use_count);

	WARN_ON(gbo->kmap.virtual);



	drm_gem_object_release(&gbo->bo.base);

}
@@ -356,18 +357,17 @@ EXPORT_SYMBOL(drm_gem_vram_kmap); 


static void drm_gem_vram_kunmap_locked(struct drm_gem_vram_object *gbo)

{

	struct ttm_bo_kmap_obj *kmap = &gbo->kmap;



	if (WARN_ON_ONCE(!gbo->kmap_use_count))

		return;

	if (--gbo->kmap_use_count > 0)

		return;



	if (!kmap->virtual)

		return;



	ttm_bo_kunmap(kmap);

	kmap->virtual = NULL;

	/*

	 * Permanently mapping and unmapping buffers adds overhead from

	 * updating the page tables and creates debugging output. Therefore,

	 * we delay the actual unmap operation until the BO gets evicted

	 * from memory. See drm_gem_vram_bo_driver_move_notify().

	 */

}



/**
@@ -497,6 +497,38 @@ int drm_gem_vram_bo_driver_verify_access(struct ttm_buffer_object *bo, 
}

EXPORT_SYMBOL(drm_gem_vram_bo_driver_verify_access);



/**

 * drm_gem_vram_bo_driver_move_notify() -

 *	Implements &struct ttm_bo_driver.move_notify

 * @bo:		TTM buffer object. Refers to &struct drm_gem_vram_object.bo

 * @evict:	True, if the BO is being evicted from graphics memory;

 *		false otherwise.

 * @new_mem:	New memory region, or NULL on destruction

 */

void drm_gem_vram_bo_driver_move_notify(struct ttm_buffer_object *bo,

					bool evict,

					struct ttm_mem_reg *new_mem)

{

	struct drm_gem_vram_object *gbo;

	struct ttm_bo_kmap_obj *kmap;



	/* TTM may pass BOs that are not GEM VRAM BOs. */

	if (!drm_is_gem_vram(bo))

		return;



	gbo = drm_gem_vram_of_bo(bo);

	kmap = &gbo->kmap;



	if (WARN_ON_ONCE(gbo->kmap_use_count))

		return;



	if (!kmap->virtual)

		return;

	ttm_bo_kunmap(kmap);

	kmap->virtual = NULL;

}

EXPORT_SYMBOL(drm_gem_vram_bo_driver_move_notify);



/*

 * drm_gem_vram_mm_funcs - Functions for &struct drm_vram_mm

 *
@@ -506,7 +538,8 @@ EXPORT_SYMBOL(drm_gem_vram_bo_driver_verify_access); 
 */

const struct drm_vram_mm_funcs drm_gem_vram_mm_funcs = {

	.evict_flags = drm_gem_vram_bo_driver_evict_flags,

	.verify_access = drm_gem_vram_bo_driver_verify_access

	.verify_access = drm_gem_vram_bo_driver_verify_access,

	.move_notify = drm_gem_vram_bo_driver_move_notify,

};

EXPORT_SYMBOL(drm_gem_vram_mm_funcs);

include/drm/drm_gem_vram_helper.h

+4 −0
Original line number Diff line number Diff line
@@ -112,6 +112,10 @@ int drm_gem_vram_fill_create_dumb(struct drm_file *file, 
void drm_gem_vram_bo_driver_evict_flags(struct ttm_buffer_object *bo,

					struct ttm_placement *pl);



void drm_gem_vram_bo_driver_move_notify(struct ttm_buffer_object *bo,

					bool evict,

					struct ttm_mem_reg *new_mem);



int drm_gem_vram_bo_driver_verify_access(struct ttm_buffer_object *bo,

					 struct file *filp);

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