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Release unneeded memory more eagerly from conhost (#10738) 

The `_CONSOLE_API_MSG` buffer is resized to cover an entire message.
Later on any UTF-8 data is cached in a separate temporary
buffer inside `til::u8state` to prevent lone surrogate pairs.

Both cases are problematic as neither buffer is freed after the read
has finished. Passing a 100MB buffer to conhost once will thus cause it
to continue using ~220MB of physical memory until the conhost process exits.

This change releases unneeded memory as soon as the requested buffer
size has halved. In practice this means that once a command has returned
all buffers will shrink, as the shell commonly sends very small messages.

## PR Checklist
* [x] Closes #10731
* [x] I work here
* [x] Tests added/passed

## Validation Steps Performed

* Buffers aren't reallocated during printing ✔️
* Buffers shrink after printing finished ✔️
This commit is contained in:
Leonard Hecker 2021-07-21 07:59:57 +02:00 committed by GitHub
parent 10b12ac90c
commit 8779249b12
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 24 additions and 2 deletions
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8
src/inc/til/u8u16convert.h
View File

@ -55,6 +55,14 @@ namespace til // Terminal Implementation Library. Also: "Today I Learned"
RETURN_HR_IF(E_ABORT, !base::CheckAdd(in.length(), _partialsLen).AssignIfValid(&capacity));
_buffer.clear();
// If we were previously called with a huge buffer we have an equally large _buffer.
// We shouldn't just keep this huge buffer around, if no one needs it anymore.
if (_buffer.capacity() > 16 * 1024 && (_buffer.capacity() >> 1) > capacity)
{
_buffer.shrink_to_fit();
}
_buffer.reserve(capacity);
// copy UTF-8 code units that were remaining from the previous call (if any)

18
src/server/ApiMessage.cpp
View File

@ -104,7 +104,14 @@ try
{
RETURN_HR_IF(E_FAIL, State.ReadOffset > Descriptor.InputSize);
ULONG const cbReadSize = Descriptor.InputSize - State.ReadOffset;
const ULONG cbReadSize = Descriptor.InputSize - State.ReadOffset;
// If we were previously called with a huge buffer we have an equally large _inputBuffer.
// We shouldn't just keep this huge buffer around, if no one needs it anymore.
if (_inputBuffer.capacity() > 16 * 1024 && (_inputBuffer.capacity() >> 1) > cbReadSize)
{
_inputBuffer.shrink_to_fit();
}
_inputBuffer.resize(cbReadSize);
@ -145,10 +152,17 @@ try
ULONG cbWriteSize = Descriptor.OutputSize - State.WriteOffset;
RETURN_IF_FAILED(ULongMult(cbWriteSize, cbFactor, &cbWriteSize));
// If we were previously called with a huge buffer we have an equally large _outputBuffer.
// We shouldn't just keep this huge buffer around, if no one needs it anymore.
if (_outputBuffer.capacity() > 16 * 1024 && (_outputBuffer.capacity() >> 1) > cbWriteSize)
{
_outputBuffer.shrink_to_fit();
}
_outputBuffer.resize(cbWriteSize);
// 0 it out.
std::fill(_outputBuffer.begin(), _outputBuffer.end(), (BYTE)0);
std::fill_n(_outputBuffer.data(), _outputBuffer.size(), BYTE(0));
State.OutputBuffer = _outputBuffer.data();
State.OutputBufferSize = cbWriteSize;