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// Copyright 2018 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/metal/DeviceMTL.h"
#include "common/GPUInfo.h"
#include "common/Platform.h"
#include "dawn_native/BackendConnection.h"
#include "dawn_native/BindGroupLayout.h"
#include "dawn_native/Commands.h"
#include "dawn_native/ErrorData.h"
#include "dawn_native/metal/BindGroupLayoutMTL.h"
#include "dawn_native/metal/BindGroupMTL.h"
#include "dawn_native/metal/BufferMTL.h"
#include "dawn_native/metal/CommandBufferMTL.h"
#include "dawn_native/metal/ComputePipelineMTL.h"
#include "dawn_native/metal/PipelineLayoutMTL.h"
#include "dawn_native/metal/QuerySetMTL.h"
#include "dawn_native/metal/QueueMTL.h"
#include "dawn_native/metal/RenderPipelineMTL.h"
#include "dawn_native/metal/SamplerMTL.h"
#include "dawn_native/metal/ShaderModuleMTL.h"
#include "dawn_native/metal/StagingBufferMTL.h"
#include "dawn_native/metal/SwapChainMTL.h"
#include "dawn_native/metal/TextureMTL.h"
#include "dawn_native/metal/UtilsMetal.h"
#include "dawn_platform/DawnPlatform.h"
#include "dawn_platform/tracing/TraceEvent.h"
#include <type_traits>
namespace dawn_native { namespace metal {
namespace {
// The time interval for each round of kalman filter
static constexpr uint64_t kFilterIntervalInMs = static_cast<uint64_t>(NSEC_PER_SEC / 10);
struct KalmanInfo {
float filterValue; // The estimation value
float kalmanGain; // The kalman gain
float R; // The covariance of the observation noise
float P; // The a posteriori estimate covariance
// A simplified kalman filter for estimating timestamp period based on measured values
float KalmanFilter(KalmanInfo* info, float measuredValue) {
// Optimize kalman gain
info->kalmanGain = info->P / (info->P + info->R);
// Correct filter value
info->filterValue =
info->kalmanGain * measuredValue + (1.0 - info->kalmanGain) * info->filterValue;
// Update estimate covariance
info->P = (1.0f - info->kalmanGain) * info->P;
return info->filterValue;
void API_AVAILABLE(macos(10.15), ios(14))
UpdateTimestampPeriod(id<MTLDevice> device,
KalmanInfo* info,
MTLTimestamp* cpuTimestampStart,
MTLTimestamp* gpuTimestampStart,
float* timestampPeriod) {
// The filter value is converged to an optimal value when the kalman gain is less than
// 0.01. At this time, the weight of the measured value is too small to change the next
// filter value, the sampling and calculations do not need to continue anymore.
if (info->kalmanGain < 0.01f) {
MTLTimestamp cpuTimestampEnd = 0, gpuTimestampEnd = 0;
[device sampleTimestamps:&cpuTimestampEnd gpuTimestamp:&gpuTimestampEnd];
// Update the timestamp start values when timestamp reset happens
if (cpuTimestampEnd < *cpuTimestampStart || gpuTimestampEnd < *gpuTimestampStart) {
*cpuTimestampStart = cpuTimestampEnd;
*gpuTimestampStart = gpuTimestampEnd;
if (cpuTimestampEnd - *cpuTimestampStart >= kFilterIntervalInMs) {
// The measured timestamp period
float measurement = (cpuTimestampEnd - *cpuTimestampStart) /
static_cast<float>(gpuTimestampEnd - *gpuTimestampStart);
// Measurement update
*timestampPeriod = KalmanFilter(info, measurement);
*cpuTimestampStart = cpuTimestampEnd;
*gpuTimestampStart = gpuTimestampEnd;
} // namespace
// static
ResultOrError<Device*> Device::Create(AdapterBase* adapter,
NSPRef<id<MTLDevice>> mtlDevice,
const DawnDeviceDescriptor* descriptor) {
Ref<Device> device = AcquireRef(new Device(adapter, std::move(mtlDevice), descriptor));
return device.Detach();
Device::Device(AdapterBase* adapter,
NSPRef<id<MTLDevice>> mtlDevice,
const DawnDeviceDescriptor* descriptor)
: DeviceBase(adapter, descriptor), mMtlDevice(std::move(mtlDevice)), mCompletedSerial(0) {
Device::~Device() {
MaybeError Device::Initialize() {
mCommandQueue.Acquire([*mMtlDevice newCommandQueue]);
if (mCommandQueue == nil) {
return DAWN_INTERNAL_ERROR("Failed to allocate MTLCommandQueue.");
if (IsFeatureEnabled(Feature::TimestampQuery)) {
// Make a best guess of timestamp period based on device vendor info, and converge it to
// an accurate value by the following calculations.
mTimestampPeriod =
gpu_info::IsIntel(GetAdapter()->GetPCIInfo().vendorId) ? 83.333f : 1.0f;
// Initialize kalman filter parameters
mKalmanInfo = std::make_unique<KalmanInfo>();
mKalmanInfo->filterValue = 0.0f;
mKalmanInfo->kalmanGain = 0.5f;
mKalmanInfo->R =
0.0001f; // The smaller this value is, the smaller the error of measured value is,
// the more we can trust the measured value.
mKalmanInfo->P = 1.0f;
if (@available(macos 10.15, iOS 14.0, *)) {
// Sample CPU timestamp and GPU timestamp for first time at device creation
[*mMtlDevice sampleTimestamps:&mCpuTimestamp gpuTimestamp:&mGpuTimestamp];
return DeviceBase::Initialize(new Queue(this));
void Device::InitTogglesFromDriver() {
bool haveStoreAndMSAAResolve = false;
if (@available(macOS 10.12, *)) {
haveStoreAndMSAAResolve =
[*mMtlDevice supportsFeatureSet:MTLFeatureSet_macOS_GPUFamily1_v2];
#elif defined(DAWN_PLATFORM_IOS)
haveStoreAndMSAAResolve =
[*mMtlDevice supportsFeatureSet:MTLFeatureSet_iOS_GPUFamily3_v2];
// On tvOS, we would need MTLFeatureSet_tvOS_GPUFamily2_v1.
SetToggle(Toggle::EmulateStoreAndMSAAResolve, !haveStoreAndMSAAResolve);
bool haveSamplerCompare = true;
#if defined(DAWN_PLATFORM_IOS)
haveSamplerCompare = [*mMtlDevice supportsFeatureSet:MTLFeatureSet_iOS_GPUFamily3_v1];
// TODO( Investigate emulation -- possibly expensive.
SetToggle(Toggle::MetalDisableSamplerCompare, !haveSamplerCompare);
bool haveBaseVertexBaseInstance = true;
#if defined(DAWN_PLATFORM_IOS)
haveBaseVertexBaseInstance =
[*mMtlDevice supportsFeatureSet:MTLFeatureSet_iOS_GPUFamily3_v1];
// TODO( Investigate emulation.
SetToggle(Toggle::DisableBaseVertex, !haveBaseVertexBaseInstance);
SetToggle(Toggle::DisableBaseInstance, !haveBaseVertexBaseInstance);
// Vertex buffer robustness is implemented by using programmable vertex pulling. Enable
// that code path if it isn't explicitly disabled.
if (IsRobustnessEnabled()) {
SetToggle(Toggle::MetalEnableVertexPulling, true);
// TODO( tighten this workaround when the driver bug is fixed.
SetToggle(Toggle::AlwaysResolveIntoZeroLevelAndLayer, true);
const PCIInfo& pciInfo = GetAdapter()->GetPCIInfo();
// TODO( Use MTLStorageModeShared instead of MTLStorageModePrivate when
// creating MTLCounterSampleBuffer in QuerySet on Intel platforms, otherwise it fails to
// create the buffer. Change to use MTLStorageModePrivate when the bug is fixed.
if (@available(macOS 10.15, iOS 14.0, *)) {
bool useSharedMode = gpu_info::IsIntel(pciInfo.vendorId);
SetToggle(Toggle::MetalUseSharedModeForCounterSampleBuffer, useSharedMode);
// TODO( r8unorm and rg8unorm textures with multiple mip levels don't
// clear properly on Intel Macs.
if (gpu_info::IsIntel(pciInfo.vendorId)) {
SetToggle(Toggle::DisableR8RG8Mipmaps, true);
// On some Intel GPU vertex only render pipeline get wrong depth result if no fragment
// shader provided. Create a dummy fragment shader module to work around this issue.
if (gpu_info::IsIntel(this->GetAdapter()->GetPCIInfo().vendorId)) {
bool useDummyFragmentShader = true;
if (gpu_info::IsSkylake(this->GetAdapter()->GetPCIInfo().deviceId)) {
useDummyFragmentShader = false;
SetToggle(Toggle::UseDummyFragmentInVertexOnlyPipeline, useDummyFragmentShader);
ResultOrError<Ref<BindGroupBase>> Device::CreateBindGroupImpl(
const BindGroupDescriptor* descriptor) {
return BindGroup::Create(this, descriptor);
ResultOrError<Ref<BindGroupLayoutBase>> Device::CreateBindGroupLayoutImpl(
const BindGroupLayoutDescriptor* descriptor,
PipelineCompatibilityToken pipelineCompatibilityToken) {
return BindGroupLayout::Create(this, descriptor, pipelineCompatibilityToken);
ResultOrError<Ref<BufferBase>> Device::CreateBufferImpl(const BufferDescriptor* descriptor) {
return Buffer::Create(this, descriptor);
ResultOrError<Ref<CommandBufferBase>> Device::CreateCommandBuffer(
CommandEncoder* encoder,
const CommandBufferDescriptor* descriptor) {
return CommandBuffer::Create(encoder, descriptor);
Ref<ComputePipelineBase> Device::CreateUninitializedComputePipelineImpl(
const ComputePipelineDescriptor* descriptor) {
return ComputePipeline::CreateUninitialized(this, descriptor);
ResultOrError<Ref<PipelineLayoutBase>> Device::CreatePipelineLayoutImpl(
const PipelineLayoutDescriptor* descriptor) {
return PipelineLayout::Create(this, descriptor);
ResultOrError<Ref<QuerySetBase>> Device::CreateQuerySetImpl(
const QuerySetDescriptor* descriptor) {
return QuerySet::Create(this, descriptor);
Ref<RenderPipelineBase> Device::CreateUninitializedRenderPipelineImpl(
const RenderPipelineDescriptor* descriptor) {
return RenderPipeline::CreateUninitialized(this, descriptor);
ResultOrError<Ref<SamplerBase>> Device::CreateSamplerImpl(const SamplerDescriptor* descriptor) {
return Sampler::Create(this, descriptor);
ResultOrError<Ref<ShaderModuleBase>> Device::CreateShaderModuleImpl(
const ShaderModuleDescriptor* descriptor,
ShaderModuleParseResult* parseResult) {
return ShaderModule::Create(this, descriptor, parseResult);
ResultOrError<Ref<SwapChainBase>> Device::CreateSwapChainImpl(
const SwapChainDescriptor* descriptor) {
return OldSwapChain::Create(this, descriptor);
ResultOrError<Ref<NewSwapChainBase>> Device::CreateSwapChainImpl(
Surface* surface,
NewSwapChainBase* previousSwapChain,
const SwapChainDescriptor* descriptor) {
return SwapChain::Create(this, surface, previousSwapChain, descriptor);
ResultOrError<Ref<TextureBase>> Device::CreateTextureImpl(const TextureDescriptor* descriptor) {
return Texture::Create(this, descriptor);
ResultOrError<Ref<TextureViewBase>> Device::CreateTextureViewImpl(
TextureBase* texture,
const TextureViewDescriptor* descriptor) {
return TextureView::Create(texture, descriptor);
void Device::InitializeComputePipelineAsyncImpl(Ref<ComputePipelineBase> computePipeline,
WGPUCreateComputePipelineAsyncCallback callback,
void* userdata) {
ComputePipeline::InitializeAsync(std::move(computePipeline), callback, userdata);
void Device::InitializeRenderPipelineAsyncImpl(Ref<RenderPipelineBase> renderPipeline,
WGPUCreateRenderPipelineAsyncCallback callback,
void* userdata) {
RenderPipeline::InitializeAsync(std::move(renderPipeline), callback, userdata);
ResultOrError<ExecutionSerial> Device::CheckAndUpdateCompletedSerials() {
uint64_t frontendCompletedSerial{GetCompletedCommandSerial()};
if (frontendCompletedSerial > mCompletedSerial) {
// sometimes we increase the serials, in which case the completed serial in
// the device base will surpass the completed serial we have in the metal backend, so we
// must update ours when we see that the completed serial from device base has
// increased.
mCompletedSerial = frontendCompletedSerial;
return ExecutionSerial(mCompletedSerial.load());
MaybeError Device::TickImpl() {
// Just run timestamp period calculation when timestamp feature is enabled.
if (IsFeatureEnabled(Feature::TimestampQuery)) {
if (@available(macos 10.15, iOS 14.0, *)) {
UpdateTimestampPeriod(GetMTLDevice(), mKalmanInfo.get(), &mCpuTimestamp,
&mGpuTimestamp, &mTimestampPeriod);
return {};
id<MTLDevice> Device::GetMTLDevice() {
return mMtlDevice.Get();
id<MTLCommandQueue> Device::GetMTLQueue() {
return mCommandQueue.Get();
CommandRecordingContext* Device::GetPendingCommandContext() {
return &mCommandContext;
MaybeError Device::SubmitPendingCommandBuffer() {
if (!mCommandContext.WasUsed()) {
return {};
// Acquire the pending command buffer, which is retained. It must be released later.
NSPRef<id<MTLCommandBuffer>> pendingCommands = mCommandContext.AcquireCommands();
// Replace mLastSubmittedCommands with the mutex held so we avoid races between the
// schedule handler and this code.
std::lock_guard<std::mutex> lock(mLastSubmittedCommandsMutex);
mLastSubmittedCommands = pendingCommands;
// Make a local copy of the pointer to the commands because it's not clear how ObjC blocks
// handle types with copy / move constructors being referenced in the block..
id<MTLCommandBuffer> pendingCommandsPointer = pendingCommands.Get();
[*pendingCommands addScheduledHandler:^(id<MTLCommandBuffer>) {
// This is DRF because we hold the mutex for mLastSubmittedCommands and pendingCommands
// is a local value (and not the member itself).
std::lock_guard<std::mutex> lock(mLastSubmittedCommandsMutex);
if (this->mLastSubmittedCommands.Get() == pendingCommandsPointer) {
this->mLastSubmittedCommands = nullptr;
// Update the completed serial once the completed handler is fired. Make a local copy of
// mLastSubmittedSerial so it is captured by value.
ExecutionSerial pendingSerial = GetLastSubmittedCommandSerial();
// this ObjC block runs on a different thread
[*pendingCommands addCompletedHandler:^(id<MTLCommandBuffer>) {
TRACE_EVENT_ASYNC_END0(GetPlatform(), GPUWork, "DeviceMTL::SubmitPendingCommandBuffer",
ASSERT(uint64_t(pendingSerial) > mCompletedSerial.load());
this->mCompletedSerial = uint64_t(pendingSerial);
TRACE_EVENT_ASYNC_BEGIN0(GetPlatform(), GPUWork, "DeviceMTL::SubmitPendingCommandBuffer",
[*pendingCommands commit];
return mCommandContext.PrepareNextCommandBuffer(*mCommandQueue);
ResultOrError<std::unique_ptr<StagingBufferBase>> Device::CreateStagingBuffer(size_t size) {
std::unique_ptr<StagingBufferBase> stagingBuffer =
std::make_unique<StagingBuffer>(size, this);
return std::move(stagingBuffer);
MaybeError Device::CopyFromStagingToBuffer(StagingBufferBase* source,
uint64_t sourceOffset,
BufferBase* destination,
uint64_t destinationOffset,
uint64_t size) {
// Metal validation layers forbid 0-sized copies, assert it is skipped prior to calling
// this function.
ASSERT(size != 0);
->EnsureDataInitializedAsDestination(GetPendingCommandContext(), destinationOffset,
id<MTLBuffer> uploadBuffer = ToBackend(source)->GetBufferHandle();
id<MTLBuffer> buffer = ToBackend(destination)->GetMTLBuffer();
[GetPendingCommandContext()->EnsureBlit() copyFromBuffer:uploadBuffer
return {};
// In Metal we don't write from the CPU to the texture directly which can be done using the
// replaceRegion function, because the function requires a non-private storage mode and Dawn
// sets the private storage mode by default for all textures except IOSurfaces on macOS.
MaybeError Device::CopyFromStagingToTexture(const StagingBufferBase* source,
const TextureDataLayout& dataLayout,
TextureCopy* dst,
const Extent3D& copySizePixels) {
Texture* texture = ToBackend(dst->texture.Get());
EnsureDestinationTextureInitialized(GetPendingCommandContext(), texture, *dst,
RecordCopyBufferToTexture(GetPendingCommandContext(), ToBackend(source)->GetBufferHandle(),
source->GetSize(), dataLayout.offset, dataLayout.bytesPerRow,
dataLayout.rowsPerImage, texture, dst->mipLevel, dst->origin,
dst->aspect, copySizePixels);
return {};
Ref<Texture> Device::CreateTextureWrappingIOSurface(const ExternalImageDescriptor* descriptor,
IOSurfaceRef ioSurface,
uint32_t plane) {
const TextureDescriptor* textureDescriptor = FromAPI(descriptor->cTextureDescriptor);
if (ConsumedError(ValidateTextureDescriptor(this, textureDescriptor))) {
return nullptr;
if (ConsumedError(
ValidateIOSurfaceCanBeWrapped(this, textureDescriptor, ioSurface, plane))) {
return nullptr;
Ref<Texture> result;
if (ConsumedError(Texture::CreateFromIOSurface(this, descriptor, ioSurface, plane),
&result)) {
return nullptr;
return result;
void Device::WaitForCommandsToBeScheduled() {
if (ConsumedError(SubmitPendingCommandBuffer())) {
// Only lock the object while we take a reference to it, otherwise we could block further
// progress if the driver calls the scheduled handler (which also acquires the lock) before
// finishing the waitUntilScheduled.
NSPRef<id<MTLCommandBuffer>> lastSubmittedCommands;
std::lock_guard<std::mutex> lock(mLastSubmittedCommandsMutex);
lastSubmittedCommands = mLastSubmittedCommands;
[*lastSubmittedCommands waitUntilScheduled];
MaybeError Device::WaitForIdleForDestruction() {
// Forget all pending commands.
// Wait for all commands to be finished so we can free resources
while (GetCompletedCommandSerial() != GetLastSubmittedCommandSerial()) {
return {};
void Device::DestroyImpl() {
ASSERT(GetState() == State::Disconnected);
// Forget all pending commands.
mCommandQueue = nullptr;
mMtlDevice = nullptr;
uint32_t Device::GetOptimalBytesPerRowAlignment() const {
return 1;
uint64_t Device::GetOptimalBufferToTextureCopyOffsetAlignment() const {
return 1;
float Device::GetTimestampPeriodInNS() const {
return mTimestampPeriod;
}} // namespace dawn_native::metal