Severe memory regression in V1

[rodperottoni]

Original issue: expo/expo#46519

Bug Description

After upgrading to Expo 56 and as a consequence Hermes v1, RAM memory usage almost doubled in my app.
I tried going back to SDK 55 and enabling the V1 Opt-In via Expo's expo-build-properties, and the memory increase is observed there too.

Steps To Reproduce

Minimal reproducible example
https://github.com/rodperottoni/expo-sdk-56-mem-regression

Steps to reproduce
I have provided an example repository with a sandbox for both Expo SDK 56 and 55. The main branch is SDK 56, and the sdk-55 branch is SDK 55.
Checkout to each branch and run npm i --force + npm run compile + npm run ios.
Then, open the performance monitor as soon as the app opens.

Findings

On SDK 56 RAM usage almost doubles in this basic example (149mb -> 266mb):

SDK 55	SDK 56

This increase is more noticeable in complex apps. In my employer's production app we've jumped from ~580mb up to 1.1GB in the home page of our app.

Further scenarios I tested:

• SDK 55 + useHermesV1: true: Increased RAM usage
  • This scenario is in the sdk-55-with-hermes-v1 branch of the example repo
• SDK 56 + useHermesV1: false: Increased RAM usage (disabling this flag seems to not do anything?)
  • This scenario is in the sdk-56-not-hermes-v1 branch of the example repo

The Expected Behavior

Memory usage to remain the same or decrease. The React Native 0.84 release notes say:

Automatic performance gains: All apps will use Hermes V1 by default, bringing improved execution speed and reduced memory usage.

[SirJalias]

I agree and looks like the culprit is hermes v1, there is this issue I opened on React native: react/react-native#57059 where there is a repository to reproduce without expo.

[tmikov]

Detailed explanation here: #1829 (comment)

To confirm, you are seeing this on iOS?

[SirJalias]

Detailed explanation here: #1829 (comment)

To confirm, you are seeing this on iOS?

In the issue I opened it was on Android, as far as I've seen happens on both platforms

[rodperottoni]

Detailed explanation here: #1829 (comment)

To confirm, you are seeing this on iOS?

Yes, only tested in iOS thus far.

[rodperottoni]

I have conducted further tests via XCode instruments on our production app and found some interesting numbers.
Test parameters: 10 seconds recording, record-on-launch, app terminated after the recording.

Expo 55 (not Hermes v1)	Expo 56 (Hermes v1)

Findings:

• Heap allocation: 60MB -> 240MB
• Dirty size: 158MB -> 261MB
• Some of the frame drops I observed in a development build of the app seem to be gone the production variant.