[PATCH v4 4/5] drm/amdgpu: use bulk moves for efficient VM LRU handling (v4)
Christian König
christian.koenig at amd.com
Tue Aug 21 13:54:28 UTC 2018
Am 21.08.2018 um 15:43 schrieb Huang Rui:
> On Mon, Aug 20, 2018 at 09:17:12PM +0800, Christian König wrote:
>> Am 20.08.2018 um 08:05 schrieb Huang Rui:
>>> On Fri, Aug 17, 2018 at 06:38:16PM +0800, Koenig, Christian wrote:
>>>> Am 17.08.2018 um 12:08 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.
>>>>>
>>>>> v2: move all BOs include idle, relocated, and moved list to the end of LRU and
>>>>> put them together.
>>>>> v3: remove unused parameter and use list_for_each_entry instead of the one with
>>>>> save entry.
>>>>> v4: move the amdgpu_vm_move_to_lru_tail after command submission, at that time,
>>>>> all bo will be back on idle list.
>>>>>
>>>>> Signed-off-by: Christian König <christian.koenig at amd.com>
>>>>> Signed-off-by: Huang Rui <ray.huang at amd.com>
>>>>> Tested-by: Mike Lothian <mike at fireburn.co.uk>
>>>>> Tested-by: Dieter Nützel <Dieter at nuetzel-hh.de>
>>>>> Acked-by: Chunming Zhou <david1.zhou at amd.com>
>>>>> ---
>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 11 ++++++
>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 71 ++++++++++++++++++++++++++--------
>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h | 11 +++++-
>>>>> 3 files changed, 75 insertions(+), 18 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>>>>> index 502b94f..9fbdf02 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>>>>> @@ -1260,6 +1260,16 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
>>>>> return 0;
>>>>> }
>>>>>
>>>>> +static void amdgpu_cs_vm_move_on_lru(struct amdgpu_device *adev,
>>>>> + struct amdgpu_cs_parser *p)
>>>>> +{
>>>>> + struct amdgpu_fpriv *fpriv = p->filp->driver_priv;
>>>>> + struct amdgpu_vm *vm = &fpriv->vm;
>>>>> +
>>>>> + if (vm->validated)
>>>> That check belongs inside amdgpu_vm_move_to_lru_tail().
>>>>
>>>>> + amdgpu_vm_move_to_lru_tail(adev, vm);
>>>>> +}
>>>>> +
>>>>> int amdgpu_cs_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
>>>>> {
>>>>> struct amdgpu_device *adev = dev->dev_private;
>>>>> @@ -1310,6 +1320,7 @@ int amdgpu_cs_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
>>>>>
>>>>> r = amdgpu_cs_submit(&parser, cs);
>>>>>
>>>>> + amdgpu_cs_vm_move_on_lru(adev, &parser);
>>>>> out:
>>>>> amdgpu_cs_parser_fini(&parser, r, reserved_buffers);
>>>>> return r;
>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>>> index 9c84770..037cfbc 100644
>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>>> @@ -268,6 +268,53 @@ void amdgpu_vm_get_pd_bo(struct amdgpu_vm *vm,
>>>>> }
>>>>>
>>>>> /**
>>>>> + * amdgpu_vm_move_to_lru_tail_by_list - move one list of BOs to end of LRU
>>>>> + *
>>>>> + * @vm: vm providing the BOs
>>>>> + * @list: the list that stored BOs
>>>>> + *
>>>>> + * Move one list of BOs to the end of LRU and update the positions.
>>>>> + */
>>>>> +static void
>>>>> +amdgpu_vm_move_to_lru_tail_by_list(struct amdgpu_vm *vm, struct list_head *list)
>>>> I don't see much of a point having a separate function for this any more.
>>>>
>>>>> +{
>>>>> + struct amdgpu_vm_bo_base *bo_base;
>>>>> +
>>>>> + list_for_each_entry(bo_base, list, 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);
>>>>> + }
>>>>> +}
>>>>> +
>>>>> +/**
>>>>> + * amdgpu_vm_move_to_lru_tail - move all BOs to the end of LRU
>>>>> + *
>>>>> + * @adev: amdgpu device pointer
>>>>> + * @vm: vm providing the BOs
>>>>> + *
>>>>> + * Move all BOs to the end of LRU and remember their positions to put them
>>>>> + * together.
>>>>> + */
>>>>> +void amdgpu_vm_move_to_lru_tail(struct amdgpu_device *adev,
>>>>> + struct amdgpu_vm *vm)
>>>>> +{
>>>>> + struct ttm_bo_global *glob = adev->mman.bdev.glob;
>>>>> +
>>>>> + memset(&vm->lru_bulk_move, 0, sizeof(vm->lru_bulk_move));
>>>>> +
>>>>> + spin_lock(&glob->lru_lock);
>>>>> + amdgpu_vm_move_to_lru_tail_by_list(vm, &vm->idle);
>>>>> + spin_unlock(&glob->lru_lock);
>>>>> +}
>>>>> +
>>>>> +/**
>>>>> * amdgpu_vm_validate_pt_bos - validate the page table BOs
>>>>> *
>>>>> * @adev: amdgpu device pointer
>>>>> @@ -288,6 +335,7 @@ int amdgpu_vm_validate_pt_bos(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>>>>> struct amdgpu_vm_bo_base *bo_base, *tmp;
>>>>> int r = 0;
>>>>>
>>>>> + vm->validated = false;
>>>> That won't work like this. It is perfectly possible that CS is aborted
>>>> because of a signal and amdgpu_vm_move_to_lru_tail() never called.
>>>>
>>>> I suggest to do "vm->validated |= !list_empty(&vm->evicted);" here and
>>>> then set it to false again in amdgpu_vm_move_to_lru_tail().
>>>>
>>>> And maybe we need a better name than "validated", maybe "bulk_moveable"
>>>> or something like that.
>>>>
>>> Actually, "validated" is opposite to "bulk_moveable".
>>> So how about use "vm->bulk_moveable = list_empty(&vm->evicted);" here
>> That still won't work correct. See the validation can be interrupted.
>>
>> So we need something like "vm->bulk_moveable &=
>> list_empty(&vm->evicted);" here.
> Thanks. I found if we use vm->bulk_moveable, it will have a corruption of list.
>
> [ 2763.834228] ------------[ cut here ]------------
> [ 2763.839221] list_del corruption. prev->next should be ffff9137dae028f8, but was ffffa59b82003ae0
> [ 2763.848330] WARNING: CPU: 1 PID: 281 at lib/list_debug.c:53 __list_del_entry_valid+0x7c/0xa0
> ...
> [ 2764.053257] Call Trace:
> [ 2764.055748] ttm_bo_del_from_lru+0x77/0xc0 [ttm]
> [ 2764.060437] ttm_bo_release+0x23a/0x2c0 [ttm]
> [ 2764.064924] amdgpu_bo_destroy+0x93/0x140 [amdgpu]
> [ 2764.069769] ttm_bo_release_list+0x113/0x170 [ttm]
> [ 2764.074695] amdgpu_bo_destroy+0x93/0x140 [amdgpu]
> [ 2764.079544] ttm_bo_release_list+0x113/0x170 [ttm]
>
> However, if use vm->bulk_not_moveable (like vm->validated), the issue is gone.
> I didn't confirm the reason yet.
Make sure that you don't try to move the root PD as well. E.g. test for
bo->parent and skip if it is NULL.
Christian.
>
> Thanks,
> Ray
>
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