events: optimize condition for optimal scenario - #20452
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Instead of always checking whether we've already warned about a possible EventEmitter memory leak, first run the rest of the code as accessing random properties on an Array is expensive.
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Can you share benchmark results? |
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@mscdex I'm not claiming it's huge or anything but it's like 1.5-2% with 100 runs. confidence improvement accuracy (*) (**) (***) events/ee-add-remove.js n=250000 *** 2.01 % ±0.74% ±0.97% ±1.25% IMO it's a pretty sensible change. The code inside the if runs anyway unless we've already emitted that warning. This way we can bail out one check earlier in all cases but the one where someone actually triggers the warning. |
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jasnell
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lib/events.js
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| process.emitWarning(w); | ||
| } | ||
| m = $getMaxListeners(target); | ||
| if (m && m > 0 && existing.length > m && !existing.warned) { |
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If you have time and inclination to test: does reducing m && m > 0 to m > 0 make a difference?
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Not sure if it makes a difference yet but it seems a harmless change and simplifies the conditional further. I don't see why we shouldn't do it.
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CI after the change proposed by @bnoordhuis: https://ci.nodejs.org/job/node-test-pull-request/14621/ |
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BridgeAR
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Instead of always checking whether we've already warned about a possible EventEmitter memory leak, first run the rest of the code as accessing random properties on an Array is expensive. In addition, remove an unnecessary truthy check. PR-URL: #20452 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
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Instead of always checking whether we've already warned about a possible EventEmitter memory leak, first run the rest of the code as accessing random properties on an Array is expensive. In addition, remove an unnecessary truthy check. PR-URL: #20452 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
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Instead of always checking whether we've already warned about a possible EventEmitter memory leak, first run the rest of the code as accessing random properties on an Array is expensive. In addition, remove an unnecessary truthy check. PR-URL: #20452 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Tobias Nießen <tniessen@tnie.de> Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
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Instead of always checking whether we've already warned about a possible EventEmitter memory leak, first run the rest of the code as accessing custom properties on an Array is decently slow.
I believe it makes more sense to optimize for well written user-code than code that is already attaching too many listeners and getting this warning, without having set a higher number of maxListeners.
I've also adjusted the benchmark to be a bit more representative as there's too much noise with the current iteration count.
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