[Performance] 6% performance improvement by lessening is_array and instanceof checks. #1845
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instanceof is a slow-ish operation, since it's a string compare, but using ->kind directly we can do a direct pointer check, which is way faster.
By doing a null check before calling is_array we prevent tons of method calls, since its very common for calling visitors to be null.
Since it common for the result to be null, by doing that check before we do the more expensive instanceof checks we can prevent allot of if checks
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Thanks, released with https://github.com/webonyx/graphql-php/releases/tag/v15.30.1. Please consider sponsoring. |
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Thanks Sven 💪 |
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Yeah, man, awesome. Keep 'em coming! |
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Respect, thanks! |
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Yeey thank you @SavageTiger :) |
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https://github.com/webonyx/graphql-php/releases/tag/v15.30.1 > Improve performance 6% by lessening is_array and instanceof checks webonyx/graphql-php#1845 Change-Id: Ica32b9e771ad4abaaa0b5c8522e5e055364df3fd
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Description
While investigating the performance of our API that runs on top of Webonyx, I made some cachegrind profiles and found that we perform an insane amount of is_array checks for each query.
The source of this is the method extractVisitFn. While investigating this, I found that if I do a null check on $kindVisitor and $specificVisitor before checking if they are arrays, it cuts down our callgraph by about 50%. It might seem a bit counterintuitive since is_array also performs the null check implicitly; however, the overhead cost of calling the method on such a hot path is pretty high.
After this finding, I did some more digging into the visitor and found that we also do a bunch of instanceof checks on the result while it is null in many cases. By doing an early null check, all those if and else-if conditions can be skipped.
Lastly, I noticed the instanceof checks in leave() in TypeInfo. instanceof is more expensive computationally than you might think since, under the hood, it’s a string comparison for which memory gets allocated. In this case, we can use ->kind due to the strict typehint.
I tested all these changes by comparing a previous benchmark run to the latest benchmark run and have seen a clear performance improvement with each consecutive change. Here is a table of the overall win:
The baseline is the current version