[Performance] Use TokenTup object pool to reduce allocations in LexFilter #8058
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cartermp
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Dec 30, 2019
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Great approach overall and love the results. Some minor things + a question.
cartermp
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Dec 31, 2019
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Awesome work and love the results.
KevinRansom
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Jan 6, 2020
nosami
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Feb 23, 2021
…lter (dotnet#8058) * not working * more fixes * fix * a change * Pool now works in lex filter * Added checks * Added comment to maxSize * Minor comment on TokenTup
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We were getting a ton of
TokenTupallocations when parsing.Image below is just a small sample of allocations of parsing one file,
TypeChecker.fs.There are never many
TokenTupobjects being used at the same time. They are created and thrown away very quickly. But, they are very large.To handle this problem, we can use an object pool. Below is the impact it had.
Before:
After:
Makes the parser faster and doesn't push objects into Gen2 so quickly. The downside is that we have to care about the lifetime of
TokenTupin theLexFilter, so it increases complexity and more prone to error - but should be caught quickly.Alternatives:
TokenTupa struct.TokenTupa struct may eliminate heap allocations, but there are a ton of copying. To fix that problem we could pass itbyref. However, this requires much larger changes and ergonomically speaking, is a lot harder to deal with.