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

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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@xxxxxxx>
> > Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
> > ---
> >   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?

        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) {
                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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