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// 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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// 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),
device->IsToggleEnabled(Toggle::UseD3D12ResidencyManagement)) {
// 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();
size, 1, &d3d12Pageable));
// Since we can't evict the heap, it's unnecessary to track the heap in the LRU Cache.
if (pageable->IsInResidencyLRUCache()) {
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) {
// If another lock still exists on the heap, nothing further should be done.
if (pageable->IsResidencyLocked()) {
// When all locks have been removed, the resource remains resident and becomes tracked in
// the corresponding LRU.
// 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:
return &mVideoMemoryInfo.nonLocal;
// 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;
return segmentInfo->externalReservation;
void ResidencyManager::UpdateVideoMemoryInfo() {
if (!mDevice->GetDeviceInfo().isUMA) {
void ResidencyManager::UpdateMemorySegmentInfo(MemorySegmentInfo* segmentInfo) {
->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) {
// 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()) {
return pageable;
MaybeError ResidencyManager::EnsureCanAllocate(uint64_t allocationSize,
MemorySegment memorySegment) {
if (!mResidencyManagementEnabled) {
return {};
uint64_t bytesEvicted;
EnsureCanMakeResident(allocationSize, GetMemorySegmentInfo(memorySegment)));
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) {
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) {
sizeEvicted += pageable->GetSize();
if (resourcesToEvict.size() > 0) {
"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()) {
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.
} else {
if (heap->GetMemorySegment() == MemorySegment::Local) {
localSizeToMakeResident += heap->GetSize();
} else {
nonLocalSizeToMakeResident += heap->GetSize();
// 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.
// Insert the heap into the appropriate LRU.
if (localSizeToMakeResident > 0) {
return MakeAllocationsResident(&mVideoMemoryInfo.local, localSizeToMakeResident,
if (nonLocalSizeToMakeResident > 0) {
return MakeAllocationsResident(&mVideoMemoryInfo.nonLocal, nonLocalSizeToMakeResident,
return {};
MaybeError ResidencyManager::MakeAllocationsResident(MemorySegmentInfo* segment,
uint64_t sizeToMakeResident,
uint64_t numberOfObjectsToMakeResident,
ID3D12Pageable** allocations) {
uint64_t bytesEvicted;
DAWN_TRY_ASSIGN(bytesEvicted, EnsureCanMakeResident(sizeToMakeResident, segment));
// 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).
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) {
"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) {
ASSERT(pageable->IsInList() == false);
// 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) {
mRestrictBudgetForTesting = true;
// 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