Originally by CodingFabian

https://dev.vaadin.com/review/#/c/3924

Originally by @Legioth

Thank you for your patch!

Originally by CodingFabian

FYI: I just did a few comparisons for a blog post.

For the same set of actions performed by a short testbench test on our application the pre-patch code was creating 9442 instances of AllChildrenIterable and 9942 instances of CombinedIterator.

After the patch it only created AbstractClientConnector$1 and AbstractClientConnector$1$1 32 times - quite a difference.

I expect most other real applications to have about the same ratio. The only component having both child components and extensions which is frequently used would be DragAndDropWrapper, I assume.

Originally by @Legioth

Sounds like very excellent results!

Do you have any measurements or guesstimates on how this change might affect actual runtime performance?

Other components that are expected to have both child components and extensions are UI and the upcoming Grid, but they are both such that you typically don't have very many instances active in the same view.

Originally by CodingFabian

Hi Leif,

no I have note done any benchmarks.
Speed wise, I think this is very minor. The old code did create objects, the new code does a bit more checking.

If you have small component trees then this change is most likely not measurable in terms of speedups. only with big trees it could give a few ms.

What it however does is to reduce the pressure on the garbage collector, which is not a problem under low load, but turns out to be a big problem under load.

There are a few other places in vaadin which do excessive object allocation, and I will work on them as soon as I have the 7.2.x upgrade done on our application.

If I look at hotspots right now it would be Connector-iteration and JSON generation (including diffing) both on client and server side. Thats why I had done a few patches for JsonCodec and related recently.