CPU usage on idle?

[mszczepanczyk]

I added checker to the build process in our app and after a while I started getting complaints about high CPU usage with webpack --watch. Interestingly only windows people raised it. I've tried to investigate the issue on my macOS and realized the checker processes use quite a lot of CPU resources even when idling:

V8 inspector attached to one of them shows no executions:

I suspect the CPU consumption is caused by GC or file watchers. Any idea how to fix/debug this one?

[piotr-oles]

Could you provide more information about your setup? The best option would be a bug reproduction repository and information about your OS and hardware. If you are not able to create bug reproduction repository, send at least your webpack config :)

[mszczepanczyk]

@piotr-oles hey, thanks for getting back!

I've tried to replicate the problem in a new repo with similar setup, and some auto-generated typescript files but the worst I'm getting so far is ~4% cpu on idle. It kind of feels like the number is slowly getting higher with more ts files but it's hard to tell as it jumps around and my dumb ad hoc generator quickly exceeds available stack size. I couldn't find any benchmark/test files that I could use though.

That said, even 4% on idle isn't nothing, especially once compared to webpack which uses zero when watching.

I'm using current node lts on macOS, cpu i5-7360U (2 cores)

Here's the repo: https://github.com/mszczepanczyk/fork-ts-checker-high-cpu-on-idle

[taylortdixon]

I'm not able to share the repository I am working on, but I am seeing this same issue, where it's getting up to 40% on idle.

System Information:
Microsoft Windows 10 Pro 10.0.14393 Build 14393
i7-6820HQ 2.70GHz 4 Cores

Dependencies:
fork-ts-checker-webpack-plugin: 1.0.1
Typescript 3.4.1
Webpack 4.29.6
happypack: 5.0.1
Ts-Loader 5.3.3

[johnnyreilly]

As part of your tweaking I suggest dropping happypack and starting to use the incremental API. Check out the config here for inspiration: https://github.com/TypeStrong/ts-loader/blob/master/examples/fork-ts-checker-webpack-plugin/webpack.config.development.js

Stopping using happypack might reduce the resource usage significantly

[delaaxe]

I have the exact same issue on Windows 10 using this via create react app v2.1.8

[ajkettun]

Same issue here (Win 10). Upgraded from 0.4.6 to 1.0.1. 1.0.1 uses about 10% CPU, 0.4.6 practically none.

[NeKJ]

@johnnyreilly

I have the same issue with my system:

Windows 10 1809 x64
Node 10.15.1
Typescript 3.4.2
Gulp 4.0.0
ts-loader 5.3.3
webpack 4.29.6

I just tried your suggestion and changed to ts-loader to transpileOnly with the useTypescriptIncrementalAPI enabled:

But unfortunately the issue remains, fork-ts-checker plugin eats 5-8% cpu (of total 4 real i7 cores) while sitting idle:

If I set instead the useTypescriptIncrementalAPI to false, then the cpu idle usage drops to 0. Therefore this is issue definitely related with this new setting.

[0xorial]

I think I had some improvement when I tried setting environmental variable TSC_NONPOLLING_WATCHER = '1'.
More info

[NeKJ]

I read the link and figured out that this is the correct setting to use:

set TSC_WATCHFILE=UseFsEvents

I tested it and indeed cpu usage on idle is 0.0% without any issues (so far) watching and recompiling the files upon change.

[johnnyreilly]

Is this PR-able? I'd be interested in baking in better default behaviour if we can.

[NeKJ]

Yeah I guess so. Probably we could also bake in a new option too, that you could switch from polling to fsevents.

[johnnyreilly]

If you'd like to try something out we'd be very grateful ❤️

[NeKJ]

sure :)

[NeKJ]

PR ready, check it out :)
#256