[PATCH] drm/amdgpu: band aid validating VM PTs

[Huang Rui]

On Wed, Jun 20, 2018 at 10:45:44PM +0800, Christian König wrote:
> Am 20.06.2018 um 13:25 schrieb Huang Rui:
> > On Tue, Jun 19, 2018 at 02:57:00PM +0200, Christian König wrote:
> >> Always validating the VM PTs takes to much time. Only always validate
> >> the per VM BOs for now.
> > Christian, you delete PTE BO instead of moving them into idle list. The
> > intention is to avoid them do evction back when do vm_validate_pt_bos,
> > right?
> 
> No, the intention is to avoid the extra command submission overhead with 
> moving them on the LRU.
> 

Thanks. I only see it's to decrease bo numbers in the lru list (man->lru).
Is the extra command submission overhead caused by many times of evcition
or bo validation cost (like the purpose of per-vm that to decrease the work
of bo list parser).

Thanks,
Ray

> This messes the LRU for VMs up a bit, but that shouldn't matter much 
> because when we need to evict PTs the performance is not relevant 
> anymore anyway.
> 
> Christian.
> 
> >
> > But in that function, I just see that it will walk over the idle list and
> > move the bo into lru list, and didn't find the evction behaviour called
> > explicitly. So why will it save the performance cost?
> >
> > Thanks,
> > Ray
> >
> >> Signed-off-by: Christian König <christian.koenig at amd.com>
> >> ---
> >>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> >> index 819949418495..7c30451ba897 100644
> >> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> >> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> >> @@ -1082,7 +1082,7 @@ int amdgpu_vm_update_directories(struct amdgpu_device *adev,
> >>   					   struct amdgpu_vm_bo_base,
> >>   					   vm_status);
> >>   		bo_base->moved = false;
> >> -		list_move(&bo_base->vm_status, &vm->idle);
> >> +		list_del_init(&bo_base->vm_status);
> >>   
> >>   		bo = bo_base->bo->parent;
> >>   		if (!bo)
> >> -- 
> >> 2.14.1
> >>
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