New React.Perf eats a lot of CPU.

[niba]

After migration to React 15.1.0 I noticed that my application is running slower than usual. Quick debug with Chrome profiler shows that method purgeUnmountedComponents from ReactComponentTreeDevtool eats around 30% of my application time. On every mouse move or click method iterates over huge amount of elements. I don't know if that behaviour is desirable.

[gaearon]

Hi! Could you try building React from master and giving it another try? I know @spicyj optimized some of this in #6770 but it hasn't been released yet.

[gaearon]

For now I’ll mark as unconfirmed, but I’m happy to look into it if you provide an example app that reproduces this.

[niba]

I have just checked it with the latest version from master and it is better.

Stil it eats around 15-20% but maybe it is connected with my shouldComponentUpdates. I need to analyze it more closely.

[gabrielenosso]

I have the same problem.
I didn't try with the "master" though.

[sophiebits]

As far as I can tell your last two screenshots don't show anything from the perf tools? The function names there all just look like normal batching/update code.

[niba]

@gaearon Thanks for help

@spicyj I know that you closed it but I observed one more thing regarding this topic.

I'm developing a map based web app where user mostly just browse and move around on the map. These actions fire a lot of map events like zoomIn, zoomOut, mapMove. Here is a screenshot from profiler after one of those session when user just browses map and doesn't use heavily react part of application. React@master(after 15.1.0) eats here about ~9% of my CPU

and now the similar session with [email protected], here we have ~3-5%

as you can see the time is much bigger in the latest version. I wanted to let you know about this

[gaearon]

But that's unrelated to ReactPerf, isn't it?
Are you measuring production builds?

[jacehensley-wf]

I am also seeing this using react.js on 15.1.0. It seems to not be an issue with react.min.js

I built react.js with "master" and the issue seems to go away.

[gaearon]

I built react.js with "master" and the issue seems to go away.

👍

Then it’s fixed in master and the fix will be out in the next release.

[niba]

@gaearon true, it is unrelated to ReactPerf, sorry for making mess, i'm beginner in open source and I need to learn a lot. In production mode times are the same so I think that the debug mode is a little heavier in the latest version.
Thanks for help!

[gaearon]

Please feel free to investigate the difference further. It might very well be that there is low hanging fruit for optimization of DEV in master.