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Lazy initialisation of LinkedList in TokenOperations constructor -> 7% performance gain for formatter by bergmeister · Pull Request #1453 · PowerShell/PSScriptAnalyzer · GitHub

Lazy initialisation of LinkedList in TokenOperations constructor -> 7% performance gain for formatter - #1453

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James Truher (JamesWTruher) merged 2 commits into
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bergmeister:formatter/speed-TokenOperationsctorLazyField
Apr 21, 2020
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Lazy initialisation of LinkedList in TokenOperations constructor -> 7% performance gain for formatter#1453
James Truher (JamesWTruher) merged 2 commits into
PowerShell:masterfrom
bergmeister:formatter/speed-TokenOperationsctorLazyField

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Christoph Bergmeister (bergmeister) commented Apr 18, 2020
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PR Summary

This is a simple optimizaton as many consumers that construct the TokenOperations class do not call APIs that use the LinkedList. This changes the CPU consumption of this class constructor during a format run from 8% to 1%. Of course one could optimize further but I suggest to do the quick wins first with little risk of code regression.
Performance gains are mainly in formatter rules but also in relatively expensive UseSupportsShouldProcess rule.

Also remove unused method. Technically this is a breaking change due to them being publicly exposed but I don't think people use them, the only usage that I can imagine is in custom rules. I did a global GitHub search and it confirmed that no one is probably using those APIs.

This class is quite disgusting overall, littered with TODOs and private/public methods spread across the file. Idea is to keep changes minimal and safe.

PR Checklist

Christoph Bergmeister added 2 commits April 18, 2020 23:47

Rob Holt (rjmholt) left a comment

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Awesome!

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Also, is there a good reason to use a linked list here? Surely it should just be a List<>?

Christoph Bergmeister (bergmeister) commented Apr 21, 2020
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Also, is there a good reason to use a linked list here? Surely it should just be a List<>?

When you look at the callers, they use the .Previous and .Next properties of a LL, which makes the code easier to read I have to say. With this we reduced the overhead from 8% to 1% so although one could optimize more, this was an easy way of achieving much without having to change to much in the spirit of the 80-20 rule. Only once other, bigger perf impacts have been optimized, I'd come back to optimize the LinkedList away completely as well or at least create it only once and then share it.

James Truher (JamesWTruher) merged commit 022009b into PowerShell:master Apr 21, 2020
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