[PATCH 4/5] drm/amdgpu: use bulk moves for efficient VM LRU handling

[Christian König]

Am 08.08.2018 um 11:59 schrieb Huang Rui:
> I continue to work for bulk moving that based on the proposal by Christian.
>
> Background:
> 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
> patch:
> "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
> workaround.
>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> Signed-off-by: Huang Rui <ray.huang at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 22 ++++++++++++++--------
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h |  4 ++++
>   2 files changed, 18 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 9c84770..eda0bb9 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -286,6 +286,7 @@ int amdgpu_vm_validate_pt_bos(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>   {
>   	struct ttm_bo_global *glob = adev->mman.bdev.glob;
>   	struct amdgpu_vm_bo_base *bo_base, *tmp;
> +	bool validated = false;
>   	int r = 0;
>   
>   	list_for_each_entry_safe(bo_base, tmp, &vm->evicted, vm_status) {
> @@ -295,14 +296,9 @@ int amdgpu_vm_validate_pt_bos(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>   			r = validate(param, bo);
>   			if (r)
>   				break;
> -
> -			spin_lock(&glob->lru_lock);
> -			ttm_bo_move_to_lru_tail(&bo->tbo, NULL);
> -			if (bo->shadow)
> -				ttm_bo_move_to_lru_tail(&bo->shadow->tbo, NULL);
> -			spin_unlock(&glob->lru_lock);
>   		}
>   
> +		validated = true;
>   		if (bo->tbo.type != ttm_bo_type_kernel) {
>   			spin_lock(&vm->moved_lock);
>   			list_move(&bo_base->vm_status, &vm->moved);
> @@ -312,6 +308,15 @@ int amdgpu_vm_validate_pt_bos(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>   		}
>   	}
>   
> +	if (!validated) {
> +		spin_lock(&glob->lru_lock);
> +		ttm_bo_bulk_move_lru_tail(&vm->lru_bulk_move);
> +		spin_unlock(&glob->lru_lock);
> +		return 0;
> +	}
> +
> +	memset(&vm->lru_bulk_move, 0, sizeof(vm->lru_bulk_move));
> +
>   	spin_lock(&glob->lru_lock);
>   	list_for_each_entry(bo_base, &vm->idle, vm_status) {
>   		struct amdgpu_bo *bo = bo_base->bo;
> @@ -319,9 +324,10 @@ int amdgpu_vm_validate_pt_bos(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>   		if (!bo->parent)
>   			continue;
>   
> -		ttm_bo_move_to_lru_tail(&bo->tbo, NULL);
> +		ttm_bo_move_to_lru_tail(&bo->tbo, &vm->lru_bulk_move);
>   		if (bo->shadow)
> -			ttm_bo_move_to_lru_tail(&bo->shadow->tbo, NULL);
> +			ttm_bo_move_to_lru_tail(&bo->shadow->tbo,
> +						&vm->lru_bulk_move);

Here is still one problem: The BOs currently evicted are not yet in the 
idle state.

So this must be moved to the end of the state machine, probably best if 
we put that into a separate function.

Regards,
Christian.

>   	}
>   	spin_unlock(&glob->lru_lock);
>   
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> index 67a15d4..92725ac 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
> @@ -29,6 +29,7 @@
>   #include <linux/rbtree.h>
>   #include <drm/gpu_scheduler.h>
>   #include <drm/drm_file.h>
> +#include <drm/ttm/ttm_bo_driver.h>
>   
>   #include "amdgpu_sync.h"
>   #include "amdgpu_ring.h"
> @@ -226,6 +227,9 @@ struct amdgpu_vm {
>   
>   	/* Some basic info about the task */
>   	struct amdgpu_task_info task_info;
> +
> +	/* Store positions of group of BOs */
> +	struct ttm_lru_bulk_move lru_bulk_move;
>   };
>   
>   struct amdgpu_vm_manager {