KTOR-7941 Fix performance on readUtfLineTo #4537
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bjhham
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Dec 9, 2024
e5l
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Dec 10, 2024
e5l
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Dec 10, 2024
| while (!isClosedForRead) { | ||
| while (!readBuffer.exhausted()) { | ||
| when (val b = readBuffer.readByte()) { | ||
| CR -> { |
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I was assuming indexOf is working faster than manual readByte
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Yeah, it's all buffered anyway so it seems to be roughly the same implementation.
Oh! I just realized why it's so slow! It's because if you have an input with no \r characters, then it would be O(n^2) for the previous implementation, because it searches to the end of the content every time!
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You mean adding a benchmark to |
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Benchmark: ktorio/ktor-benchmarks#49 |
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Subsystem
Core, I/O
Motivation
KTOR-7941 A Performance issue reading with ByteReadChannel.readUTF8LineTo request body
Solution
When reading input that is missing either CR or LF characters, the current implementation will read the full buffer for every line, which leads to a
O(n^2)performance, which is very bad for this kind of operation when there are many newlines with only\nfor example.