[PATCH 0/5] drm/ttm,amdgpu: Introduce LRU bulk move functionality

Huang Rui ray.huang at amd.com
Wed Aug 8 09:59:32 UTC 2018

The idea and proposal is originally from Christian, and I continue to work to
deliver it.

amdgpu driver will move all PD/PT and PerVM BOs into idle list. Then move all of
them on the end of LRU list one by one. Thus, that cause so many BOs moved to
the end of the LRU, and impact performance seriously.

Then Christian provided a workaround to not move PD/PT BOs on LRU with below
"drm/amdgpu: band aid validating VM PTs"
Commit 0bbf32026cf5ba41e9922b30e26e1bed1ecd38ae

However, the final solution should bulk move all PD/PT and PerVM BOs on the LRU
instead of one by one.

Whenever amdgpu_vm_validate_pt_bos() is called and we have BOs which need to be
validated we move all BOs together to the end of the LRU without dropping the
lock for the LRU.

While doing so we note the beginning and end of this block in the LRU list.

Now when amdgpu_vm_validate_pt_bos() is called and we don't have anything to do,
we don't move every BO one by one, but instead cut the LRU list into pieces so
that we bulk move everything to the end in just one operation.

Test data:
|              |The Talos        |Clpeak(OCL)|BusSpeedReadback(OCL)                  |
|              |Principle(Vulkan)|           |                                       |
|              |                 |           |0.319 ms(1k) 0.314 ms(2K) 0.308 ms(4K) |
| Original     |  147.7 FPS      |  76.86 us |0.307 ms(8K) 0.310 ms(16K)             |
| Orignial + WA|                 |           |0.254 ms(1K) 0.241 ms(2K)              |
|(don't move   |  162.1 FPS      |  42.15 us |0.230 ms(4K) 0.223 ms(8K) 0.204 ms(16K)|
|PT BOs on LRU)|                 |           |                                       |
| Bulk move    |  163.1 FPS      |  40.52 us |0.244 ms(1K) 0.252 ms(2K) 0.213 ms(4K) |
|              |                 |           |0.214 ms(8K) 0.225 ms(16K)             |

After test them with above three benchmarks include vulkan and opencl. We can
see the visible improvement than original, and even better than original with


Christian K├Ânig (2):
  drm/ttm: add helper structures for bulk moves on lru list
  drm/ttm: revise ttm_bo_move_to_lru_tail to support bulk moves

Huang Rui (3):
  drm/ttm: add bulk move function on LRU
  drm/amdgpu: use bulk moves for efficient VM LRU handling
  drm/amdgpu: move PD/PT bos on LRU again

 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 24 +++++++----
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h |  4 ++
 drivers/gpu/drm/ttm/ttm_bo.c           | 78 +++++++++++++++++++++++++++++++++-
 include/drm/ttm/ttm_bo_api.h           | 16 ++++++-
 include/drm/ttm/ttm_bo_driver.h        | 28 ++++++++++++
 5 files changed, 139 insertions(+), 11 deletions(-)


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