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Evaluating “ReadLine using System.IO.Pipelines” Performance in C# — Part 2

Joni 【ジョニー】
Full-Stack Web Dev. Early adopter. C#/.NET technology lover.
Originally published at Medium on ・2 min read

Evaluating “ReadLine using System.IO.Pipelines” Performance in C# — Part 2

Read string line by line using System.IO.Pipelines API in C

On part 1 of this series, I concluded:

In terms of speed, it is surprisingly slower than the ordinary ReadLine version given the string length ≤ 80 (perhaps I am doing it wrong? Let me know! I am still learning!). It is starting to shine, getting faster and faster if the string length ≥ 90. (270% 🚀 faster for string length = 1000).

I decided to take a further look and added more patterns to the benchmarks. The new code, instead of blindly using SequenceReader, is a mix of fast ReadOnlySpan and slow SequenceReader; by inspecting ReadOnlySequence.IsSingleSegment property.

The idea is, get a Span once and then pull as many lines as possible out of it before moving to the next segment of the sequence, as also pointed out by a generous Reddit user u/scalablecory, thanks! (apparently a member of the .NET Team?!)

Here is the result:

As you can see, it performs well under every test case, rendering my previous conclusion obsolete!!!

And here is the gist version:

Noticed that this time it has fewer test cases; I reduced some LineCharMultiplier variations, as I don’t think we need it.

You can find the source code in my GitHub repository.


  • Pipelines versions are better in terms of memory usage (using less memory).
  • In terms of speed, it is 103% ~ 333% 🚀🚀🚀 faster, depends on the string length.
  • Less GC pressure (a good thing) for Pipelines versions (Gen 0, Gen 1).
  • The amount of code to write for the Pipelines version is super longer!

DISCLAIMER: Your mileage may vary. As with all performance work, each of the scenarios chosen for your application should be measured, measured and measured. There is no silver bullet.

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