Re: [PATCH 2/9] drm/ttm: move the LRU into resource handling v3

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Am 09.02.22 um 11:09 schrieb Matthew Auld:
On Wed, 9 Feb 2022 at 08:41, Christian König
<ckoenig.leichtzumerken@xxxxxxxxx> wrote:
This way we finally fix the problem that new resource are
not immediately evict-able after allocation.

That has caused numerous problems including OOM on GDS handling
and not being able to use TTM as general resource manager.

v2: stop assuming in ttm_resource_fini that res->bo is still valid.
v3: cleanup kerneldoc, add more lockdep annotation

Signed-off-by: Christian König <christian.koenig@xxxxxxx>
Tested-by: Bas Nieuwenhuizen <bas@xxxxxxxxxxxxxxxxxxx>
---
  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c  |   8 +-
  drivers/gpu/drm/i915/gem/i915_gem_ttm.c |   2 +-
  drivers/gpu/drm/ttm/ttm_bo.c            | 115 ++--------------------
  drivers/gpu/drm/ttm/ttm_bo_util.c       |   1 -
  drivers/gpu/drm/ttm/ttm_device.c        |  64 ++++++-------
  drivers/gpu/drm/ttm/ttm_resource.c      | 122 +++++++++++++++++++++++-
  include/drm/ttm/ttm_bo_api.h            |  16 ----
  include/drm/ttm/ttm_bo_driver.h         |  29 +-----
  include/drm/ttm/ttm_resource.h          |  35 +++++++
  9 files changed, 197 insertions(+), 195 deletions(-)
<snip>

  /**
   * ttm_resource_init - resource object constructure
   * @bo: buffer object this resources is allocated for
@@ -52,10 +156,12 @@ void ttm_resource_init(struct ttm_buffer_object *bo,
         res->bus.is_iomem = false;
         res->bus.caching = ttm_cached;
         res->bo = bo;
+       INIT_LIST_HEAD(&res->lru);

         man = ttm_manager_type(bo->bdev, place->mem_type);
         spin_lock(&bo->bdev->lru_lock);
         man->usage += bo->base.size;
+       ttm_resource_move_to_lru_tail(res, NULL);
         spin_unlock(&bo->bdev->lru_lock);
  }
  EXPORT_SYMBOL(ttm_resource_init);
@@ -66,15 +172,21 @@ EXPORT_SYMBOL(ttm_resource_init);
   * @res: the resource to clean up
   *
   * Should be used by resource manager backends to clean up the TTM resource
- * objects before freeing the underlying structure. Counterpart of
- * &ttm_resource_init
+ * objects before freeing the underlying structure. Makes sure the resource is
+ * removed from the LRU before destruction.
+ * Counterpart of &ttm_resource_init.
   */
  void ttm_resource_fini(struct ttm_resource_manager *man,
                        struct ttm_resource *res)
  {
-       spin_lock(&man->bdev->lru_lock);
-       man->usage -= res->bo->base.size;
-       spin_unlock(&man->bdev->lru_lock);
+       struct ttm_device *bdev = man->bdev;
+
+       spin_lock(&bdev->lru_lock);
+       list_del_init(&res->lru);
+       if (res->bo && bdev->funcs->del_from_lru_notify)
+               bdev->funcs->del_from_lru_notify(res->bo);
+       man->usage -= res->num_pages << PAGE_SHIFT;
Above we are using the bo->base.size for tracking usage, but here we
are using num_pages. Is it guaranteed that bo->base.size is always
page aligned? Do we need some kind of WARN_ON()? Perhaps also sanity
checking that usage == 0 when tearing down the man?

Good point, going to add that and consistently using res->num_pages for both.

Thanks,
Christian.



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