[PATCH] drm/amdgpu: Optimize recursion in amdgpu_vm_update_level
Christian König
deathsimple at vodafone.de
Thu Jul 13 13:45:58 UTC 2017
Am 12.07.2017 um 21:38 schrieb Felix Kuehling:
> On 17-07-12 03:50 AM, Christian König wrote:
>>
>> That optimization is unnecessary.
>>
>> I have a patch in the pipeline that makes the VM BO permanently CPU
>> mapped and also fixes a couple of bugs in those code path.
> You mean just for the CPU-update path? I think deferring the SDMA IB
> allocation still makes sense. In fact that's the code path I tested.
I've added tracking if we need to update anything to all paths, not just
the CPU update path.
>> Give me a moment to clean that up and send it out.
> Sure. BTW, I found that the most expensive operation turned out to be
> amdgpu_vm_move_pt_bos_in_lru. It has to recurse through all PT BOs and
> does lots of redundant list pointer manipulations for two lists (LRU and
> swap), and kref get/put.
Yeah, that's why I've stopped using the separate remove/add functions
and wanted to optimize just moving everything to the end.
But that turned out to be more problematic than I thought.
> For KFD VMs I'm removing the call to it. I think it's useless for us.
>
> amdgpu_vm_validate_pt_bos is also expensive, but not as bad because it's
> only done if there was an eviction.
>
> I was thinking about ways to optimize this. It should be possible to
> allocate multiple PTBs and PDBs in a single BO in amdgpu_vm_alloc_pts.
> That would potentially save lots of time in vm_move_pt_bos and
> vm_validate. What do you think?
I think allocating separate BOs is still the right approach, a single BO
is tricky to allocate and probably won't worth it.
Instead I move the LRU handling after the validation. So BOs are only
moved in the LRU when there actually was some eviction.
Since we don't care what kind of eviction it was this basically turns
LRU handling on/off based on memory pressure (e.g. evictions).
Regards,
Christian.
>
> Regards,
> Felix
>
>> Regards,
>> Christian.
>>
>>> ---
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 109
>>> +++++++++++++++++----------------
>>> 1 file changed, 55 insertions(+), 54 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> index ff5de3a..23b899b 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> @@ -1025,7 +1025,7 @@ static int amdgpu_vm_update_level(struct
>>> amdgpu_device *adev,
>>> {
>>> struct amdgpu_bo *shadow;
>>> struct amdgpu_ring *ring = NULL;
>>> - uint64_t pd_addr, shadow_addr = 0;
>>> + uint64_t pd_addr = 0, shadow_addr = 0;
>>> uint32_t incr = amdgpu_vm_bo_size(adev, level + 1);
>>> uint64_t last_pde = ~0, last_pt = ~0, last_shadow = ~0;
>>> unsigned count = 0, pt_idx, ndw = 0;
>>> @@ -1044,48 +1044,19 @@ static int amdgpu_vm_update_level(struct
>>> amdgpu_device *adev,
>>> WARN_ON(vm->use_cpu_for_update && shadow);
>>> if (vm->use_cpu_for_update && !shadow) {
>>> - r = amdgpu_bo_kmap(parent->bo, (void **)&pd_addr);
>>> - if (r)
>>> - return r;
>>> - r = amdgpu_vm_bo_wait(adev, parent->bo);
>>> - if (unlikely(r)) {
>>> - amdgpu_bo_kunmap(parent->bo);
>>> - return r;
>>> - }
>>> + /* Defer kmapping until it's actually needed. Some
>>> + * PDBs may need no update at all
>>> + */
>>> params.func = amdgpu_vm_cpu_set_ptes;
>>> + params.ib = (void *)(long)-1;
>>> } else {
>>> - if (shadow) {
>>> - r = amdgpu_ttm_bind(&shadow->tbo, &shadow->tbo.mem);
>>> - if (r)
>>> - return r;
>>> - }
>>> - ring = container_of(vm->entity.sched, struct amdgpu_ring,
>>> - sched);
>>> -
>>> - /* padding, etc. */
>>> - ndw = 64;
>>> -
>>> - /* assume the worst case */
>>> - ndw += parent->last_entry_used * 6;
>>> -
>>> - pd_addr = amdgpu_bo_gpu_offset(parent->bo);
>>> -
>>> - if (shadow) {
>>> - shadow_addr = amdgpu_bo_gpu_offset(shadow);
>>> - ndw *= 2;
>>> - } else {
>>> - shadow_addr = 0;
>>> - }
>>> -
>>> - r = amdgpu_job_alloc_with_ib(adev, ndw * 4, &job);
>>> - if (r)
>>> - return r;
>>> -
>>> - params.ib = &job->ibs[0];
>>> + /* Defer IB allocation until it's actually
>>> + * needed. Some PDBs may need no update at all
>>> + */
>>> + params.ib = NULL;
>>> params.func = amdgpu_vm_do_set_ptes;
>>> }
>>> -
>>> /* walk over the address space and update the directory */
>>> for (pt_idx = 0; pt_idx <= parent->last_entry_used; ++pt_idx) {
>>> struct amdgpu_bo *bo = parent->entries[pt_idx].bo;
>>> @@ -1094,22 +1065,53 @@ static int amdgpu_vm_update_level(struct
>>> amdgpu_device *adev,
>>> if (bo == NULL)
>>> continue;
>>> - if (bo->shadow) {
>>> - struct amdgpu_bo *pt_shadow = bo->shadow;
>>> -
>>> - r = amdgpu_ttm_bind(&pt_shadow->tbo,
>>> - &pt_shadow->tbo.mem);
>>> - if (r)
>>> - return r;
>>> - }
>>> -
>>> - pt = amdgpu_bo_gpu_offset(bo);
>>> - pt = amdgpu_gart_get_vm_pde(adev, pt);
>>> + pt = amdgpu_gart_get_vm_pde(adev, bo->tbo.offset);
>>> if (parent->entries[pt_idx].addr == pt)
>>> continue;
>>> parent->entries[pt_idx].addr = pt;
>>> + if (!params.ib) {
>>> + if (shadow) {
>>> + r = amdgpu_ttm_bind(&shadow->tbo,
>>> + &shadow->tbo.mem);
>>> + if (r)
>>> + return r;
>>> + }
>>> +
>>> + ring = container_of(vm->entity.sched,
>>> + struct amdgpu_ring, sched);
>>> +
>>> + /* padding, etc. */
>>> + ndw = 64;
>>> +
>>> + /* assume the worst case */
>>> + ndw += (parent->last_entry_used - pt_idx) * 6;
>>> +
>>> + pd_addr = parent->bo->tbo.offset;
>>> +
>>> + if (shadow) {
>>> + shadow_addr = shadow->tbo.offset;
>>> + ndw *= 2;
>>> + } else {
>>> + shadow_addr = 0;
>>> + }
>>> + r = amdgpu_job_alloc_with_ib(adev, ndw * 4, &job);
>>> + if (r)
>>> + return r;
>>> +
>>> + params.ib = &job->ibs[0];
>>> + } else if (!pd_addr) {
>>> + r = amdgpu_bo_kmap(parent->bo, (void **)&pd_addr);
>>> + if (r)
>>> + return r;
>>> + r = amdgpu_vm_bo_wait(adev, parent->bo);
>>> + if (unlikely(r)) {
>>> + amdgpu_bo_kunmap(parent->bo);
>>> + return r;
>>> + }
>>> + }
>>> +
>>> pde = pd_addr + pt_idx * 8;
>>> if (((last_pde + 8 * count) != pde) ||
>>> ((last_pt + incr * count) != pt) ||
>>> @@ -1148,9 +1150,9 @@ static int amdgpu_vm_update_level(struct
>>> amdgpu_device *adev,
>>> if (params.func == amdgpu_vm_cpu_set_ptes)
>>> amdgpu_bo_kunmap(parent->bo);
>>> - else if (params.ib->length_dw == 0) {
>>> + else if (params.ib && params.ib->length_dw == 0) {
>>> amdgpu_job_free(job);
>>> - } else {
>>> + } else if (params.ib) {
>>> amdgpu_ring_pad_ib(ring, params.ib);
>>> amdgpu_sync_resv(adev, &job->sync, parent->bo->tbo.resv,
>>> AMDGPU_FENCE_OWNER_VM);
>>> @@ -1166,8 +1168,7 @@ static int amdgpu_vm_update_level(struct
>>> amdgpu_device *adev,
>>> amdgpu_bo_fence(parent->bo, fence, true);
>>> dma_fence_put(vm->last_dir_update);
>>> - vm->last_dir_update = dma_fence_get(fence);
>>> - dma_fence_put(fence);
>>> + vm->last_dir_update = fence;
>>> }
>>> /*
>>> * Recurse into the subdirectories. This recursion is harmless
>>> because
>>> @@ -1176,7 +1177,7 @@ static int amdgpu_vm_update_level(struct
>>> amdgpu_device *adev,
>>> for (pt_idx = 0; pt_idx <= parent->last_entry_used; ++pt_idx) {
>>> struct amdgpu_vm_pt *entry = &parent->entries[pt_idx];
>>> - if (!entry->bo)
>>> + if (!entry->bo || !entry->entries)
>>> continue;
>>> r = amdgpu_vm_update_level(adev, vm, entry, level + 1);
>>
More information about the amd-gfx
mailing list