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

["Christian König" <christian.koenig-5C7GfCeVMHo@public.gmane.org>]

Am 09.08.2018 um 14:25 schrieb Huang Rui:
> On Thu, Aug 09, 2018 at 03:18:55PM +0800, Koenig, Christian wrote:
>> Am 09.08.2018 um 08:18 schrieb Huang Rui:
>>> On Wed, Aug 08, 2018 at 06:47:49PM +0800, Christian König wrote:
>>>> 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@amd.com>
>>>>> Signed-off-by: Huang Rui <ray.huang@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.
>>>>
>>> Thanks, so the evicted BOs should be behind the BOs in idle list that in
>>> the group between (first, last) of bulk_move_pos, right?
>> The order doesn't matter.
>>
>>>           spin_lock(&glob->lru_lock);
>>>           list_for_each_entry(bo_base, &vm->idle, vm_status) {
>>>                   struct amdgpu_bo *bo = bo_base->bo;
>>>
>>>                   if (!bo->parent)
>>>                           continue;
>>>
>>>                   ttm_bo_move_to_lru_tail(&bo->tbo, &vm->lru_bulk_move);
>>>                   if (bo->shadow)
>>>                           ttm_bo_move_to_lru_tail(&bo->shadow->tbo,
>>>                                                   &vm->lru_bulk_move);
>>>           }
>>>           list_for_each_entry_safe(bo_base, tmp, &vm->evicted, vm_status) {
>> That won't work. The BOs get removed from the evicted list when they are
>> validated.
>>
>> You need to walk both the relocated as well as the moved list here.
>>
> Is that because, at the start of the function, we already walk the evicted
> list, and some of BOs are validated and move to moved or relocated list, so
> here we need also walk both of them to make them together for bulk move?

Yes, exactly.

Alternatively you can add a new function which is called after command 
submission is done to move everything on the LRU.

At this point all BOs should now be on the idle list again and you only 
need to walk that one.

Regards,
Christian.

>
> Thanks,
> Ray
>
>> Christian.
>>
>>>                   struct amdgpu_bo *bo = bo_base->bo;
>>>                   if (!bo)
>>>                           continue;
>>>
>>>                   ttm_bo_move_to_lru_tail(&bo->tbo, &vm->lru_bulk_move);
>>>                   if (bo->shadow)
>>>                           ttm_bo_move_to_lru_tail(&bo->shadow->tbo,
>>>                                                   &vm->lru_bulk_move);
>>>           }
>>>           spin_unlock(&glob->lru_lock);
>>>
>>> Thanks,
>>> Ray
>>>
>>>> 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 {

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