Image.asset will block UI thread when load large image #58572

[zljj0818]

std::vector<uint8_t> data(mapping->GetSize()) consume much time to initialize large arrary

[fluttergithubbot]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie on the #hackers channel in Chat.

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here with @googlebot I signed it! and we'll verify it.

---

What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

ℹ️ Googlers: Go here for more info.

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project (if not, look below for help). Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

📝 Please visit https://cla.developers.google.com/ to sign.

Once you've signed (or fixed any issues), please reply here with @googlebot I signed it! and we'll verify it.

---

What to do if you already signed the CLA

Individual signers

• It's possible we don't have your GitHub username or you're using a different email address on your commit. Check your existing CLA data and verify that your email is set on your git commits.

Corporate signers

• Your company has a Point of Contact who decides which employees are authorized to participate. Ask your POC to be added to the group of authorized contributors. If you don't know who your Point of Contact is, direct the Google project maintainer to go/cla#troubleshoot (Public version).
• The email used to register you as an authorized contributor must be the email used for the Git commit. Check your existing CLA data and verify that your email is set on your git commits.
• The email used to register you as an authorized contributor must also be attached to your GitHub account.

ℹ️ Googlers: Go here for more info.

[zljj0818]

@googlebot I signed it!

[zljj0818]

@liyuqian I had signed CLA, why cla/google always failed?

[liyuqian]

It's probably because of an email address mismatch. Your commit has an author email of "[email protected]". Can you please double check that's email signed the CLA? If not, you can change your commit email: https://help.github.com/en/github/setting-up-and-managing-your-github-user-account/setting-your-commit-email-address

[liyuqian]

It would be nice to add a microbenchmark to test PlatformMessageResponseDart with a 3MB asset. See, e.g., the benchmark in https://github.com/flutter/engine/blob/master/shell/common/shell_benchmarks.cc

[liyuqian]

The memset seems to be unnecessary?

[zljj0818]

It would be nice to add a microbenchmark to test PlatformMessageResponseDart with a 3MB asset. See, e.g., the benchmark in https://github.com/flutter/engine/blob/master/shell/common/shell_benchmarks.cc

PlatformMessageResponseDart only post a ui task, and this ui task will consume time when execute

[zljj0818]

The memset seems to be unnecessary?

Yes, just according to the logical of std::vector

[liyuqian]

This if branch is unnecessary as we're always calling memcpy: whether inside ToByteData, or inside the else branch, or inside the old WrapByteData(std::unique_ptr<fml::Mapping> mapping) function.

[liyuqian]

I think this DataWrapper would be unnecessary if we just use ToByteData's implementation inside WrapByteData:

Dart_Handle WrapByteData(std::unique_ptr<fml::Mapping> mapping) {
  Dart_Handle data_handle =
      Dart_NewTypedData(Dart_TypedData_kByteData, mapping->GetSize());
  if (Dart_IsError(data_handle))
    return data_handle;

  Dart_TypedData_Type type;
  void* data = nullptr;
  intptr_t num_bytes = 0;
  FML_CHECK(!Dart_IsError(
      Dart_TypedDataAcquireData(data_handle, &type, &data, &num_bytes)));

  memcpy(data, buffer.data(), num_bytes);
  Dart_TypedDataReleaseData(data_handle);
  return data_handle;
}

[zljj0818]

I intend to optimze according to orignal code. The origial code if if (data.size() < kMessageCopyThreshold) , it will use dart vm heap to allocate data, else it use application heap to alloate data, dart vm only use DataWrapper pointer.
If use ToByteData will consume more dart vm heap.

[jason-simmons]

The platform message Dart ByteData objects can be allocated with the Tonic library that the engine uses to wrap the Dart API.

I've created a proposed PR: #18838

The version of WrapByteData within PlatformMessageResponseDart that takes a std::vector dates back to an older implementation of PlatformMessageResponseDart::Complete where the message was held in a std::vector. That version of WrapByteData would transfer the vector's buffer over to a Dart external typed data object without copying.

Later PlatformMessageResponseDart::Complete was changed to provide the message as an fml::Mapping. The fml::Mapping data must always be copied into a buffer whose lifetime is controlled by Dart. Thus WrapByteData is obsolete and can be replaced by tonic::DartByteData::Create.

[zljj0818]

ok, but it will use more dart vm heap?

[jason-simmons]

#18838 will allocate small objects on the Dart VM heap and will use a malloc buffer for large objects. This appears to be the best performance tradeoff given how Dart implements Dart_NewTypedData and Dart_NewExternalTypedData.

[zljj0818]

ok, close this PR