src/dawn_native/d3d12/ResidencyManagerD3D12.cpp - dawn - Git at Google

 // Copyright 2020 The Dawn Authors
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 #include "dawn_native/d3d12/ResidencyManagerD3D12.h"

 #include "dawn_native/d3d12/AdapterD3D12.h"
 #include "dawn_native/d3d12/D3D12Error.h"
 #include "dawn_native/d3d12/DeviceD3D12.h"
 #include "dawn_native/d3d12/Forward.h"
 #include "dawn_native/d3d12/HeapD3D12.h"

 namespace dawn_native { namespace d3d12 {

     ResidencyManager::ResidencyManager(Device* device)
         : mDevice(device),
           mResidencyManagementEnabled(
               device->IsToggleEnabled(Toggle::UseD3D12ResidencyManagement)) {
         UpdateVideoMemoryInfo();
     }

     // Increments number of locks on a heap to ensure the heap remains resident.
     MaybeError ResidencyManager::LockAllocation(Pageable* pageable) {
         if (!mResidencyManagementEnabled) {
             return {};
         }

         // If the heap isn't already resident, make it resident.
         if (!pageable->IsInResidencyLRUCache() && !pageable->IsResidencyLocked()) {
             ID3D12Pageable* d3d12Pageable = pageable->GetD3D12Pageable();
             uint64_t size = pageable->GetSize();

             DAWN_TRY(MakeAllocationsResident(GetMemorySegmentInfo(pageable->GetMemorySegment()),
                                              size, 1, &d3d12Pageable));
         }

         // Since we can't evict the heap, it's unnecessary to track the heap in the LRU Cache.
         if (pageable->IsInResidencyLRUCache()) {
             pageable->RemoveFromList();
         }

         pageable->IncrementResidencyLock();

         return {};
     }

     // Decrements number of locks on a heap. When the number of locks becomes zero, the heap is
     // inserted into the LRU cache and becomes eligible for eviction.
     void ResidencyManager::UnlockAllocation(Pageable* pageable) {
         if (!mResidencyManagementEnabled) {
             return;
         }

         ASSERT(pageable->IsResidencyLocked());
         ASSERT(!pageable->IsInResidencyLRUCache());
         pageable->DecrementResidencyLock();

         // If another lock still exists on the heap, nothing further should be done.
         if (pageable->IsResidencyLocked()) {
             return;
         }

         // When all locks have been removed, the resource remains resident and becomes tracked in
         // the corresponding LRU.
         TrackResidentAllocation(pageable);
     }

     // Returns the appropriate MemorySegmentInfo for a given MemorySegment.
     ResidencyManager::MemorySegmentInfo* ResidencyManager::GetMemorySegmentInfo(
         MemorySegment memorySegment) {
         switch (memorySegment) {
             case MemorySegment::Local:
                 return &mVideoMemoryInfo.local;
             case MemorySegment::NonLocal:
                 ASSERT(!mDevice->GetDeviceInfo().isUMA);
                 return &mVideoMemoryInfo.nonLocal;
             default:
                 UNREACHABLE();
         }
     }

     // Allows an application component external to Dawn to cap Dawn's residency budgets to prevent
     // competition for device memory. Returns the amount of memory reserved, which may be less
     // that the requested reservation when under pressure.
     uint64_t ResidencyManager::SetExternalMemoryReservation(MemorySegment segment,
                                                             uint64_t requestedReservationSize) {
         MemorySegmentInfo* segmentInfo = GetMemorySegmentInfo(segment);

         segmentInfo->externalRequest = requestedReservationSize;

         UpdateMemorySegmentInfo(segmentInfo);

         return segmentInfo->externalReservation;
     }

     void ResidencyManager::UpdateVideoMemoryInfo() {
         UpdateMemorySegmentInfo(&mVideoMemoryInfo.local);
         if (!mDevice->GetDeviceInfo().isUMA) {
             UpdateMemorySegmentInfo(&mVideoMemoryInfo.nonLocal);
         }
     }

     void ResidencyManager::UpdateMemorySegmentInfo(MemorySegmentInfo* segmentInfo) {
         DXGI_QUERY_VIDEO_MEMORY_INFO queryVideoMemoryInfo;

         ToBackend(mDevice->GetAdapter())
             ->GetHardwareAdapter()
             ->QueryVideoMemoryInfo(0, segmentInfo->dxgiSegment, &queryVideoMemoryInfo);

         // The video memory budget provided by QueryVideoMemoryInfo is defined by the operating
         // system, and may be lower than expected in certain scenarios. Under memory pressure, we
         // cap the external reservation to half the available budget, which prevents the external
         // component from consuming a disproportionate share of memory and ensures that Dawn can
         // continue to make forward progress. Note the choice to halve memory is arbitrarily chosen
         // and subject to future experimentation.
         segmentInfo->externalReservation =
             std::min(queryVideoMemoryInfo.Budget / 2, segmentInfo->externalRequest);

         segmentInfo->usage = queryVideoMemoryInfo.CurrentUsage - segmentInfo->externalReservation;

         // If we're restricting the budget for testing, leave the budget as is.
         if (mRestrictBudgetForTesting) {
             return;
         }

         // We cap Dawn's budget to 95% of the provided budget. Leaving some budget unused
         // decreases fluctuations in the operating-system-defined budget, which improves stability
         // for both Dawn and other applications on the system. Note the value of 95% is arbitrarily
         // chosen and subject to future experimentation.
         static constexpr float kBudgetCap = 0.95;
         segmentInfo->budget =
             (queryVideoMemoryInfo.Budget - segmentInfo->externalReservation) * kBudgetCap;
     }

     // Removes a heap from the LRU and returns the least recently used heap when possible. Returns
     // nullptr when nothing further can be evicted.
     ResultOrError<Pageable*> ResidencyManager::RemoveSingleEntryFromLRU(
         MemorySegmentInfo* memorySegment) {
         // If the LRU is empty, return nullptr to allow execution to continue. Note that fully
         // emptying the LRU is undesirable, because it can mean either 1) the LRU is not accurately
         // accounting for Dawn's GPU allocations, or 2) a component external to Dawn is using all of
         // the process budget and starving Dawn, which will cause thrash.
         if (memorySegment->lruCache.empty()) {
             return nullptr;
         }

         Pageable* pageable = memorySegment->lruCache.head()->value();

         ExecutionSerial lastSubmissionSerial = pageable->GetLastSubmission();

         // If the next candidate for eviction was inserted into the LRU during the current serial,
         // it is because more memory is being used in a single command list than is available.
         // In this scenario, we cannot make any more resources resident and thrashing must occur.
         if (lastSubmissionSerial == mDevice->GetPendingCommandSerial()) {
             return nullptr;
         }

         // We must ensure that any previous use of a resource has completed before the resource can
         // be evicted.
         if (lastSubmissionSerial > mDevice->GetCompletedCommandSerial()) {
             DAWN_TRY(mDevice->WaitForSerial(lastSubmissionSerial));
         }

         pageable->RemoveFromList();
         return pageable;
     }

     MaybeError ResidencyManager::EnsureCanAllocate(uint64_t allocationSize,
                                                    MemorySegment memorySegment) {
         if (!mResidencyManagementEnabled) {
             return {};
         }

         uint64_t bytesEvicted;
         DAWN_TRY_ASSIGN(bytesEvicted,
                         EnsureCanMakeResident(allocationSize, GetMemorySegmentInfo(memorySegment)));
         DAWN_UNUSED(bytesEvicted);

         return {};
     }

     // Any time we need to make something resident, we must check that we have enough free memory to
     // make the new object resident while also staying within budget. If there isn't enough
     // memory, we should evict until there is. Returns the number of bytes evicted.
     ResultOrError<uint64_t> ResidencyManager::EnsureCanMakeResident(
         uint64_t sizeToMakeResident,
         MemorySegmentInfo* memorySegment) {
         ASSERT(mResidencyManagementEnabled);

         UpdateMemorySegmentInfo(memorySegment);

         uint64_t memoryUsageAfterMakeResident = sizeToMakeResident + memorySegment->usage;

         // Return when we can call MakeResident and remain under budget.
         if (memoryUsageAfterMakeResident < memorySegment->budget) {
             return 0;
         }

         std::vector<ID3D12Pageable*> resourcesToEvict;
         uint64_t sizeNeededToBeUnderBudget = memoryUsageAfterMakeResident - memorySegment->budget;
         uint64_t sizeEvicted = 0;
         while (sizeEvicted < sizeNeededToBeUnderBudget) {
             Pageable* pageable;
             DAWN_TRY_ASSIGN(pageable, RemoveSingleEntryFromLRU(memorySegment));

             // If no heap was returned, then nothing more can be evicted.
             if (pageable == nullptr) {
                 break;
             }

             sizeEvicted += pageable->GetSize();
             resourcesToEvict.push_back(pageable->GetD3D12Pageable());
         }

         if (resourcesToEvict.size() > 0) {
             DAWN_TRY(CheckHRESULT(
                 mDevice->GetD3D12Device()->Evict(resourcesToEvict.size(), resourcesToEvict.data()),
                 "Evicting resident heaps to free memory"));
         }

         return sizeEvicted;
     }

     // Given a list of heaps that are pending usage, this function will estimate memory needed,
     // evict resources until enough space is available, then make resident any heaps scheduled for
     // usage.
     MaybeError ResidencyManager::EnsureHeapsAreResident(Heap** heaps, size_t heapCount) {
         if (!mResidencyManagementEnabled) {
             return {};
         }

         std::vector<ID3D12Pageable*> localHeapsToMakeResident;
         std::vector<ID3D12Pageable*> nonLocalHeapsToMakeResident;
         uint64_t localSizeToMakeResident = 0;
         uint64_t nonLocalSizeToMakeResident = 0;

         ExecutionSerial pendingCommandSerial = mDevice->GetPendingCommandSerial();
         for (size_t i = 0; i < heapCount; i++) {
             Heap* heap = heaps[i];

             // Heaps that are locked resident are not tracked in the LRU cache.
             if (heap->IsResidencyLocked()) {
                 continue;
             }

             if (heap->IsInResidencyLRUCache()) {
                 // If the heap is already in the LRU, we must remove it and append again below to
                 // update its position in the LRU.
                 heap->RemoveFromList();
             } else {
                 if (heap->GetMemorySegment() == MemorySegment::Local) {
                     localSizeToMakeResident += heap->GetSize();
                     localHeapsToMakeResident.push_back(heap->GetD3D12Pageable());
                 } else {
                     nonLocalSizeToMakeResident += heap->GetSize();
                     nonLocalHeapsToMakeResident.push_back(heap->GetD3D12Pageable());
                 }
             }

             // If we submit a command list to the GPU, we must ensure that heaps referenced by that
             // command list stay resident at least until that command list has finished execution.
             // Setting this serial unnecessarily can leave the LRU in a state where nothing is
             // eligible for eviction, even though some evictions may be possible.
             heap->SetLastSubmission(pendingCommandSerial);

             // Insert the heap into the appropriate LRU.
             TrackResidentAllocation(heap);
         }

         if (localSizeToMakeResident > 0) {
             return MakeAllocationsResident(&mVideoMemoryInfo.local, localSizeToMakeResident,
                                            localHeapsToMakeResident.size(),
                                            localHeapsToMakeResident.data());
         }

         if (nonLocalSizeToMakeResident > 0) {
             ASSERT(!mDevice->GetDeviceInfo().isUMA);
             return MakeAllocationsResident(&mVideoMemoryInfo.nonLocal, nonLocalSizeToMakeResident,
                                            nonLocalHeapsToMakeResident.size(),
                                            nonLocalHeapsToMakeResident.data());
         }

         return {};
     }

     MaybeError ResidencyManager::MakeAllocationsResident(MemorySegmentInfo* segment,
                                                          uint64_t sizeToMakeResident,
                                                          uint64_t numberOfObjectsToMakeResident,
                                                          ID3D12Pageable** allocations) {
         uint64_t bytesEvicted;
         DAWN_TRY_ASSIGN(bytesEvicted, EnsureCanMakeResident(sizeToMakeResident, segment));
         DAWN_UNUSED(bytesEvicted);

         // Note that MakeResident is a synchronous function and can add a significant
         // overhead to command recording. In the future, it may be possible to decrease this
         // overhead by using MakeResident on a secondary thread, or by instead making use of
         // the EnqueueMakeResident function (which is not available on all Windows 10
         // platforms).
         HRESULT hr =
             mDevice->GetD3D12Device()->MakeResident(numberOfObjectsToMakeResident, allocations);

         // A MakeResident call can fail if there's not enough available memory. This
         // could occur when there's significant fragmentation or if the allocation size
         // estimates are incorrect. We may be able to continue execution by evicting some
         // more memory and calling MakeResident again.
         while (FAILED(hr)) {
             constexpr uint32_t kAdditonalSizeToEvict = 50000000;  // 50MB

             uint64_t sizeEvicted = 0;

             DAWN_TRY_ASSIGN(sizeEvicted, EnsureCanMakeResident(kAdditonalSizeToEvict, segment));

             // If nothing can be evicted after MakeResident has failed, we cannot continue
             // execution and must throw a fatal error.
             if (sizeEvicted == 0) {
                 return DAWN_OUT_OF_MEMORY_ERROR(
                     "MakeResident has failed due to excessive video memory usage.");
             }

             hr =
                 mDevice->GetD3D12Device()->MakeResident(numberOfObjectsToMakeResident, allocations);
         }

         return {};
     }

     // Inserts a heap at the bottom of the LRU. The passed heap must be resident or scheduled to
     // become resident within the current serial. Failing to call this function when an allocation
     // is implicitly made resident will cause the residency manager to view the allocation as
     // non-resident and call MakeResident - which will make D3D12's internal residency refcount on
     // the allocation out of sync with Dawn.
     void ResidencyManager::TrackResidentAllocation(Pageable* pageable) {
         if (!mResidencyManagementEnabled) {
             return;
         }

         ASSERT(pageable->IsInList() == false);
         GetMemorySegmentInfo(pageable->GetMemorySegment())->lruCache.Append(pageable);
     }

     // Places an artifical cap on Dawn's budget so we can test in a predictable manner. If used,
     // this function must be called before any resources have been created.
     void ResidencyManager::RestrictBudgetForTesting(uint64_t artificialBudgetCap) {
         ASSERT(mVideoMemoryInfo.nonLocal.lruCache.empty());
         ASSERT(!mRestrictBudgetForTesting);

         mRestrictBudgetForTesting = true;
         UpdateVideoMemoryInfo();

         // Dawn has a non-zero memory usage even before any resources have been created, and this
         // value can vary depending on the environment Dawn is running in. By adding this in
         // addition to the artificial budget cap, we can create a predictable and reproducible
         // budget for testing.
         mVideoMemoryInfo.local.budget = mVideoMemoryInfo.local.usage + artificialBudgetCap;
         if (!mDevice->GetDeviceInfo().isUMA) {
             mVideoMemoryInfo.nonLocal.budget =
                 mVideoMemoryInfo.nonLocal.usage + artificialBudgetCap;
         }
     }

 }}  // namespace dawn_native::d3d12
	// Copyright 2020 The Dawn Authors
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	#include "dawn_native/d3d12/ResidencyManagerD3D12.h"

	#include "dawn_native/d3d12/AdapterD3D12.h"
	#include "dawn_native/d3d12/D3D12Error.h"
	#include "dawn_native/d3d12/DeviceD3D12.h"
	#include "dawn_native/d3d12/Forward.h"
	#include "dawn_native/d3d12/HeapD3D12.h"

	namespace dawn_native { namespace d3d12 {

	ResidencyManager::ResidencyManager(Device* device)
	: mDevice(device),
	mResidencyManagementEnabled(
	device->IsToggleEnabled(Toggle::UseD3D12ResidencyManagement)) {
	UpdateVideoMemoryInfo();
	}

	// Increments number of locks on a heap to ensure the heap remains resident.
	MaybeError ResidencyManager::LockAllocation(Pageable* pageable) {
	if (!mResidencyManagementEnabled) {
	return {};
	}

	// If the heap isn't already resident, make it resident.
	if (!pageable->IsInResidencyLRUCache() && !pageable->IsResidencyLocked()) {
	ID3D12Pageable* d3d12Pageable = pageable->GetD3D12Pageable();
	uint64_t size = pageable->GetSize();

	DAWN_TRY(MakeAllocationsResident(GetMemorySegmentInfo(pageable->GetMemorySegment()),
	size, 1, &d3d12Pageable));
	}

	// Since we can't evict the heap, it's unnecessary to track the heap in the LRU Cache.
	if (pageable->IsInResidencyLRUCache()) {
	pageable->RemoveFromList();
	}

	pageable->IncrementResidencyLock();

	return {};
	}

	// Decrements number of locks on a heap. When the number of locks becomes zero, the heap is
	// inserted into the LRU cache and becomes eligible for eviction.
	void ResidencyManager::UnlockAllocation(Pageable* pageable) {
	if (!mResidencyManagementEnabled) {
	return;
	}

	ASSERT(pageable->IsResidencyLocked());
	ASSERT(!pageable->IsInResidencyLRUCache());
	pageable->DecrementResidencyLock();

	// If another lock still exists on the heap, nothing further should be done.
	if (pageable->IsResidencyLocked()) {
	return;
	}

	// When all locks have been removed, the resource remains resident and becomes tracked in
	// the corresponding LRU.
	TrackResidentAllocation(pageable);
	}

	// Returns the appropriate MemorySegmentInfo for a given MemorySegment.
	ResidencyManager::MemorySegmentInfo* ResidencyManager::GetMemorySegmentInfo(
	MemorySegment memorySegment) {
	switch (memorySegment) {
	case MemorySegment::Local:
	return &mVideoMemoryInfo.local;
	case MemorySegment::NonLocal:
	ASSERT(!mDevice->GetDeviceInfo().isUMA);
	return &mVideoMemoryInfo.nonLocal;
	default:
	UNREACHABLE();
	}
	}

	// Allows an application component external to Dawn to cap Dawn's residency budgets to prevent
	// competition for device memory. Returns the amount of memory reserved, which may be less
	// that the requested reservation when under pressure.
	uint64_t ResidencyManager::SetExternalMemoryReservation(MemorySegment segment,
	uint64_t requestedReservationSize) {
	MemorySegmentInfo* segmentInfo = GetMemorySegmentInfo(segment);

	segmentInfo->externalRequest = requestedReservationSize;

	UpdateMemorySegmentInfo(segmentInfo);

	return segmentInfo->externalReservation;
	}

	void ResidencyManager::UpdateVideoMemoryInfo() {
	UpdateMemorySegmentInfo(&mVideoMemoryInfo.local);
	if (!mDevice->GetDeviceInfo().isUMA) {
	UpdateMemorySegmentInfo(&mVideoMemoryInfo.nonLocal);
	}
	}

	void ResidencyManager::UpdateMemorySegmentInfo(MemorySegmentInfo* segmentInfo) {
	DXGI_QUERY_VIDEO_MEMORY_INFO queryVideoMemoryInfo;

	ToBackend(mDevice->GetAdapter())
	->GetHardwareAdapter()
	->QueryVideoMemoryInfo(0, segmentInfo->dxgiSegment, &queryVideoMemoryInfo);

	// The video memory budget provided by QueryVideoMemoryInfo is defined by the operating
	// system, and may be lower than expected in certain scenarios. Under memory pressure, we
	// cap the external reservation to half the available budget, which prevents the external
	// component from consuming a disproportionate share of memory and ensures that Dawn can
	// continue to make forward progress. Note the choice to halve memory is arbitrarily chosen
	// and subject to future experimentation.
	segmentInfo->externalReservation =
	std::min(queryVideoMemoryInfo.Budget / 2, segmentInfo->externalRequest);

	segmentInfo->usage = queryVideoMemoryInfo.CurrentUsage - segmentInfo->externalReservation;

	// If we're restricting the budget for testing, leave the budget as is.
	if (mRestrictBudgetForTesting) {
	return;
	}

	// We cap Dawn's budget to 95% of the provided budget. Leaving some budget unused
	// decreases fluctuations in the operating-system-defined budget, which improves stability
	// for both Dawn and other applications on the system. Note the value of 95% is arbitrarily
	// chosen and subject to future experimentation.
	static constexpr float kBudgetCap = 0.95;
	segmentInfo->budget =
	(queryVideoMemoryInfo.Budget - segmentInfo->externalReservation) * kBudgetCap;
	}

	// Removes a heap from the LRU and returns the least recently used heap when possible. Returns
	// nullptr when nothing further can be evicted.
	ResultOrError<Pageable*> ResidencyManager::RemoveSingleEntryFromLRU(
	MemorySegmentInfo* memorySegment) {
	// If the LRU is empty, return nullptr to allow execution to continue. Note that fully
	// emptying the LRU is undesirable, because it can mean either 1) the LRU is not accurately
	// accounting for Dawn's GPU allocations, or 2) a component external to Dawn is using all of
	// the process budget and starving Dawn, which will cause thrash.
	if (memorySegment->lruCache.empty()) {
	return nullptr;
	}

	Pageable* pageable = memorySegment->lruCache.head()->value();

	ExecutionSerial lastSubmissionSerial = pageable->GetLastSubmission();

	// If the next candidate for eviction was inserted into the LRU during the current serial,
	// it is because more memory is being used in a single command list than is available.
	// In this scenario, we cannot make any more resources resident and thrashing must occur.
	if (lastSubmissionSerial == mDevice->GetPendingCommandSerial()) {
	return nullptr;
	}

	// We must ensure that any previous use of a resource has completed before the resource can
	// be evicted.
	if (lastSubmissionSerial > mDevice->GetCompletedCommandSerial()) {
	DAWN_TRY(mDevice->WaitForSerial(lastSubmissionSerial));
	}

	pageable->RemoveFromList();
	return pageable;
	}

	MaybeError ResidencyManager::EnsureCanAllocate(uint64_t allocationSize,
	MemorySegment memorySegment) {
	if (!mResidencyManagementEnabled) {
	return {};
	}

	uint64_t bytesEvicted;
	DAWN_TRY_ASSIGN(bytesEvicted,
	EnsureCanMakeResident(allocationSize, GetMemorySegmentInfo(memorySegment)));
	DAWN_UNUSED(bytesEvicted);

	return {};
	}

	// Any time we need to make something resident, we must check that we have enough free memory to
	// make the new object resident while also staying within budget. If there isn't enough
	// memory, we should evict until there is. Returns the number of bytes evicted.
	ResultOrError<uint64_t> ResidencyManager::EnsureCanMakeResident(
	uint64_t sizeToMakeResident,
	MemorySegmentInfo* memorySegment) {
	ASSERT(mResidencyManagementEnabled);

	UpdateMemorySegmentInfo(memorySegment);

	uint64_t memoryUsageAfterMakeResident = sizeToMakeResident + memorySegment->usage;

	// Return when we can call MakeResident and remain under budget.
	if (memoryUsageAfterMakeResident < memorySegment->budget) {
	return 0;
	}

	std::vector<ID3D12Pageable*> resourcesToEvict;
	uint64_t sizeNeededToBeUnderBudget = memoryUsageAfterMakeResident - memorySegment->budget;
	uint64_t sizeEvicted = 0;
	while (sizeEvicted < sizeNeededToBeUnderBudget) {
	Pageable* pageable;
	DAWN_TRY_ASSIGN(pageable, RemoveSingleEntryFromLRU(memorySegment));

	// If no heap was returned, then nothing more can be evicted.
	if (pageable == nullptr) {
	break;
	}

	sizeEvicted += pageable->GetSize();
	resourcesToEvict.push_back(pageable->GetD3D12Pageable());
	}

	if (resourcesToEvict.size() > 0) {
	DAWN_TRY(CheckHRESULT(
	mDevice->GetD3D12Device()->Evict(resourcesToEvict.size(), resourcesToEvict.data()),
	"Evicting resident heaps to free memory"));
	}

	return sizeEvicted;
	}

	// Given a list of heaps that are pending usage, this function will estimate memory needed,
	// evict resources until enough space is available, then make resident any heaps scheduled for
	// usage.
	MaybeError ResidencyManager::EnsureHeapsAreResident(Heap** heaps, size_t heapCount) {
	if (!mResidencyManagementEnabled) {
	return {};
	}

	std::vector<ID3D12Pageable*> localHeapsToMakeResident;
	std::vector<ID3D12Pageable*> nonLocalHeapsToMakeResident;
	uint64_t localSizeToMakeResident = 0;
	uint64_t nonLocalSizeToMakeResident = 0;

	ExecutionSerial pendingCommandSerial = mDevice->GetPendingCommandSerial();
	for (size_t i = 0; i < heapCount; i++) {
	Heap* heap = heaps[i];

	// Heaps that are locked resident are not tracked in the LRU cache.
	if (heap->IsResidencyLocked()) {
	continue;
	}

	if (heap->IsInResidencyLRUCache()) {
	// If the heap is already in the LRU, we must remove it and append again below to
	// update its position in the LRU.
	heap->RemoveFromList();
	} else {
	if (heap->GetMemorySegment() == MemorySegment::Local) {
	localSizeToMakeResident += heap->GetSize();
	localHeapsToMakeResident.push_back(heap->GetD3D12Pageable());
	} else {
	nonLocalSizeToMakeResident += heap->GetSize();
	nonLocalHeapsToMakeResident.push_back(heap->GetD3D12Pageable());
	}
	}

	// If we submit a command list to the GPU, we must ensure that heaps referenced by that
	// command list stay resident at least until that command list has finished execution.
	// Setting this serial unnecessarily can leave the LRU in a state where nothing is
	// eligible for eviction, even though some evictions may be possible.
	heap->SetLastSubmission(pendingCommandSerial);

	// Insert the heap into the appropriate LRU.
	TrackResidentAllocation(heap);
	}

	if (localSizeToMakeResident > 0) {
	return MakeAllocationsResident(&mVideoMemoryInfo.local, localSizeToMakeResident,
	localHeapsToMakeResident.size(),
	localHeapsToMakeResident.data());
	}

	if (nonLocalSizeToMakeResident > 0) {
	ASSERT(!mDevice->GetDeviceInfo().isUMA);
	return MakeAllocationsResident(&mVideoMemoryInfo.nonLocal, nonLocalSizeToMakeResident,
	nonLocalHeapsToMakeResident.size(),
	nonLocalHeapsToMakeResident.data());
	}

	return {};
	}

	MaybeError ResidencyManager::MakeAllocationsResident(MemorySegmentInfo* segment,
	uint64_t sizeToMakeResident,
	uint64_t numberOfObjectsToMakeResident,
	ID3D12Pageable** allocations) {
	uint64_t bytesEvicted;
	DAWN_TRY_ASSIGN(bytesEvicted, EnsureCanMakeResident(sizeToMakeResident, segment));
	DAWN_UNUSED(bytesEvicted);

	// Note that MakeResident is a synchronous function and can add a significant
	// overhead to command recording. In the future, it may be possible to decrease this
	// overhead by using MakeResident on a secondary thread, or by instead making use of
	// the EnqueueMakeResident function (which is not available on all Windows 10
	// platforms).
	HRESULT hr =
	mDevice->GetD3D12Device()->MakeResident(numberOfObjectsToMakeResident, allocations);

	// A MakeResident call can fail if there's not enough available memory. This
	// could occur when there's significant fragmentation or if the allocation size
	// estimates are incorrect. We may be able to continue execution by evicting some
	// more memory and calling MakeResident again.
	while (FAILED(hr)) {
	constexpr uint32_t kAdditonalSizeToEvict = 50000000; // 50MB

	uint64_t sizeEvicted = 0;

	DAWN_TRY_ASSIGN(sizeEvicted, EnsureCanMakeResident(kAdditonalSizeToEvict, segment));

	// If nothing can be evicted after MakeResident has failed, we cannot continue
	// execution and must throw a fatal error.
	if (sizeEvicted == 0) {
	return DAWN_OUT_OF_MEMORY_ERROR(
	"MakeResident has failed due to excessive video memory usage.");
	}

	hr =
	mDevice->GetD3D12Device()->MakeResident(numberOfObjectsToMakeResident, allocations);
	}

	return {};
	}

	// Inserts a heap at the bottom of the LRU. The passed heap must be resident or scheduled to
	// become resident within the current serial. Failing to call this function when an allocation
	// is implicitly made resident will cause the residency manager to view the allocation as
	// non-resident and call MakeResident - which will make D3D12's internal residency refcount on
	// the allocation out of sync with Dawn.
	void ResidencyManager::TrackResidentAllocation(Pageable* pageable) {
	if (!mResidencyManagementEnabled) {
	return;
	}

	ASSERT(pageable->IsInList() == false);
	GetMemorySegmentInfo(pageable->GetMemorySegment())->lruCache.Append(pageable);
	}

	// Places an artifical cap on Dawn's budget so we can test in a predictable manner. If used,
	// this function must be called before any resources have been created.
	void ResidencyManager::RestrictBudgetForTesting(uint64_t artificialBudgetCap) {
	ASSERT(mVideoMemoryInfo.nonLocal.lruCache.empty());
	ASSERT(!mRestrictBudgetForTesting);

	mRestrictBudgetForTesting = true;
	UpdateVideoMemoryInfo();

	// Dawn has a non-zero memory usage even before any resources have been created, and this
	// value can vary depending on the environment Dawn is running in. By adding this in
	// addition to the artificial budget cap, we can create a predictable and reproducible
	// budget for testing.
	mVideoMemoryInfo.local.budget = mVideoMemoryInfo.local.usage + artificialBudgetCap;
	if (!mDevice->GetDeviceInfo().isUMA) {
	mVideoMemoryInfo.nonLocal.budget =
	mVideoMemoryInfo.nonLocal.usage + artificialBudgetCap;
	}
	}

	}} // namespace dawn_native::d3d12