Avoid allocations in BeginAsyncPacketRead #12039
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Pull Request Overview
This PR optimizes the asynchronous packet read process by caching delegate callbacks and reusing a field to store the packet length, thereby reducing allocations.
- Cached delegates for header and body read callbacks to avoid repeated delegate creation.
- Replaced tuple allocations in BeginRead calls by storing the packet length in a field that is reused across asynchronous operations.
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| // Ensures the buffer is at least this length. | ||
| // It avoids reallocations if the buffer is already large enough. | ||
| _readBufferMemoryStream.SetLength(packetLength); | ||
| _readBufferMemoryStream.SetLength(_currentPacketLength); | ||
| byte[] packetData = _readBufferMemoryStream.GetBuffer(); | ||
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| _pipeStream.BeginRead(packetData, 0, packetLength, BodyReadComplete, new Tuple<byte[], int>(packetData, packetLength)); | ||
| _pipeStream.BeginRead(packetData, 0, _currentPacketLength, _bodyReadCompleteCallback, this); |
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Using the shared field '_currentPacketLength' for asynchronous operations assumes that read operations are strictly sequential. It would be safer to capture the packet length in a local variable to prevent potential race conditions if multiple reads were ever initiated concurrently.
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rainersigwald
approved these changes
Jun 20, 2025
…rndt/packetReadAllocs # Conflicts: # src/Build/BackEnd/Components/Communications/NodeProviderOutOfProcBase.cs
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Context
We can avoid a few allocations in the
BeginAsyncPacketRead()path. There are repeated delegate creations that can be reused, and there is some state that is used inBodyReadComplete()that we can get without allocating.There are ~40MB of allocations of
AsyncCallbackand ~10MB of Tuple allocations
We can avoid these allocations by reusing the delegates and storing the state that's used in
BodyReadComplete()(just the packet length) as a field.Changes Made
Testing
Notes