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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: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reported-and-tested-by: Davidlohr Bueso <dbueso@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20190906122056.32018-5-tzimmermann@suse.de
alistair/sunxi64-5.5-dsi
Thomas Zimmermann 2019-09-06 14:20:56 +02:00
parent f3309105b8
commit 2236439bc6
2 changed files with 45 additions and 8 deletions
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49
drivers/gpu/drm/drm_gem_vram_helper.c
View File

@ -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);

4
include/drm/drm_gem_vram_helper.h
View File

@ -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);