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Dibes | 6 years ago

They harp a lot on how fast it starts up - which sounds great - but I would like to have some solid numbers on what that startup time actually is on actual devices! I can't seem to find anything perusing around the GH page or the site

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acoates|6 years ago

We have done some internal tests of Hermes on a RN experience within Microsoft Office on Android.

Currently we use V8 with bytecode caching on Android, since it provided better startup performance than the JSC engine that normally ships within RN. So the baseline is likely already faster than stock RN.

V8 runtime Memory Impact: 30MB Hermes runtime memory impact: 21.5MB

V8 time to interaction: 1.4s Hermes time to interaction: 1.1s

We have done similar experiments on a full react-native-windows application, replacing the Chakra JS engine (also already with bytecode so faster than stock RN) with Hermes and had app boot time on a low end device go from 3.8s to 3.1s.

cztomsik|6 years ago

It's a pity the Proxy is not supported mobx is really much nicer approach to state management and usually, apps using mobx are much faster - simply because implementing shouldComponentUpdate properly is hard

snek|6 years ago

Very nice numbers, although worth mentioning hermes only appears to support es5, so there's way less stuff to load.

writepub|6 years ago

From your numbers:

1. runtime memory reduction: ~25%

2. Boot time reduction: 20%

3. Time to interaction reduction: 20%

For apps with significant boot times, and runtime memory consumption, this is valuable.