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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 i

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.

writepub 7y 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.
- r1nkgrl 7y ago
  For apps with significant boot times, and runtime memory consumption, this is valuable. This assumes that the reductions are purely proportional to the total and not (at least partially) fixed.
acostin 7y ago
Have you also compared it with v8-lite? https://chromium.googlesource.com/v8/v8/+/84450a2239672109bcf537d6740b8babda521567 https://chromium.googlesource.com/v8/v8/+/84450a2239672109bc...
- ricardobeat 7y ago
  Since it's optimized for reducing memory consumption, you'd expect it to make boot time worse?
hashseed 7y ago
Impressive numbers. Did you try to use startup snapshot in V8 to improve TTI? https://v8.dev/blog/custom-startup-snapshots https://v8.dev/blog/custom-startup-snapshots
snek 7y ago
Very nice numbers, although worth mentioning hermes only appears to support es5, so there's way less stuff to load.
- simscitizen 7y ago
  Hermes compiles JS ahead of time to bytecode. The VM takes bytecode in as input, not source code. The ES5 vs. ES6 distinction doesn't matter as much as in other engines where the runtime takes source code as input, and as a result has to pay the more expensive ES6 parsing cost at runtime.
cztomsik 7y 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
- wbercx 7y ago
  You could still use MobX 4 though. It's equally well maintained.

writepub 7y 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.

r1nkgrl 7y ago
For apps with significant boot times, and runtime memory consumption, this is valuable. This assumes that the reductions are purely proportional to the total and not (at least partially) fixed.

acostin 7y ago

Have you also compared it with v8-lite? https://chromium.googlesource.com/v8/v8/+/84450a2239672109bcf537d6740b8babda521567 https://chromium.googlesource.com/v8/v8/+/84450a2239672109bc...

ricardobeat 7y ago
Since it's optimized for reducing memory consumption, you'd expect it to make boot time worse?

hashseed 7y ago

Impressive numbers. Did you try to use startup snapshot in V8 to improve TTI? https://v8.dev/blog/custom-startup-snapshots https://v8.dev/blog/custom-startup-snapshots

snek 7y ago

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

simscitizen 7y ago
Hermes compiles JS ahead of time to bytecode. The VM takes bytecode in as input, not source code. The ES5 vs. ES6 distinction doesn't matter as much as in other engines where the runtime takes source code as input, and as a result has to pay the more expensive ES6 parsing cost at runtime.

cztomsik 7y 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

wbercx 7y ago
You could still use MobX 4 though. It's equally well maintained.