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The change looks good, but I'm a little surprised it caused such regressions. It looks like CreateFromElement is also using this constructor but before that is checking ValueKind against the same three cases above. Those branches were enough to cause significant regressions? This must be a super hot path?
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It's in the hot path for the lazy conversion of
JsonArray
andJsonObject
fromJsonElement
backed to List and dictionary backed, which is what regressed by this change.There was a problem hiding this comment.
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I wonder if the
ref readonly
parameter in the removed method contributed to the regression somehow.There was a problem hiding this comment.
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My guess is that it calls
element.ValueKind
twice, which resolves as followsplus a small cost to run the switch statement in
internal static JsonValueKind ToValueKind(this JsonTokenType tokenType)
Which is quite a lot of indirection. Possibly changing
CreateFromElement
to create a localJsonValueKind kind = element.ValueKind;
to avoid running the above twice? But still maybe running it once is even a lot here.There was a problem hiding this comment.
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Created a PR here #104108