Remove custom Hermes config for Android #31900

Ashoat · 2021-07-25T09:03:09Z

Summary

Right now, react-native on Android passes in an explicit Hermes config when initializes Hermes. The upcoming version of Hermes shipping with React Native 0.66 will handle this default config itself, so there's no need to override it from Android anymore.

Test Plan

I compiled and ran a React Native app using the Android build, making sure to build ReactAndroid from source. I confirmed that the config was actually being applied by testing how much memory an application could eat before being killed.

pull-bot · 2021-07-25T09:14:10Z

	Messages
📖	📋 Missing Changelog - Can you add a Changelog? To do so, add a "## Changelog" section to your PR description. A changelog entry has the following format: `[CATEGORY] [TYPE] - Message`. CATEGORY may be: General iOS Android JavaScript Internal (for changes that do not need to be called out in the release notes) TYPE may be: Added, for new features. Changed, for changes in existing functionality. Deprecated, for soon-to-be removed features. Removed, for now removed features. Fixed, for any bug fixes. Security, in case of vulnerabilities. MESSAGE may answer "what and why" on a feature level. Use this to briefly tell React Native users about notable changes.

Generated by 🚫 dangerJS against 0fdf5fe

analysis-bot · 2021-07-25T09:33:09Z

Platform	Engine	Arch	Size (bytes)	Diff
ios	-	universal	n/a	--

Base commit: f3e8ea9

analysis-bot · 2021-07-25T09:40:50Z

Platform	Engine	Arch	Size (bytes)	Diff
android	hermes	arm64-v8a	9,186,090	-62,773
android	hermes	armeabi-v7a	8,711,672	-56,120
android	hermes	x86	9,627,783	-63,683
android	hermes	x86_64	9,594,870	-64,321
android	jsc	arm64-v8a	10,822,153	-62,165
android	jsc	armeabi-v7a	9,739,008	-55,506
android	jsc	x86	10,859,247	-63,078
android	jsc	x86_64	11,467,856	-63,705

Base commit: f3e8ea9

Huxpro · 2021-07-28T01:02:26Z

Thanks for pulling this off! Let me cite my comments at facebook/hermes#511 (comment) for whom coming through here:

I'm wondering would it make more sense to just increase the default number within Hermes and remove the React-Android specific GCConfig in React Native instead? As more platforms (Windows, macOS) adopting Hermes, it seems suboptimal to glue this default GCConfig again and again.

Ashoat · 2021-08-06T21:15:22Z

Okay, with that approach in mind I think we can break down the work into three parts:

Right now react-native always passes in a config when it calls hermes::makeHermesRuntime. We should update it so it doesn't pass in a config unless there is a custom one being specified. That way, Hermes will be able to determine a default config on its own.
While iOS does not bother specifying a custom config currently, Android does. If we want both platforms to defer to Hermes for the default config, we should remove the custom Android config.
Finally, Hermes need to be updated to specify the default config that is currently being used for Android. (This change should be synced with change 2.)

This PR has been updated to handle 1. I can submit a follow-up PR to handle 2, but I'll need some help with 3 since I'm not familiar with how to compile and test a custom Hermes build on iOS and Android. If anybody has any pointers that would be great. Alternately, would be happy if somebody else offers to handle 3 :)

Ashoat · 2021-08-08T19:05:38Z

Rebased and tests are all looking clear! I think this is ready for review/merge. Adding some folks:

@Huxpro on the Hermes side
@alloy who wrote HermesExecutorFactory.cpp, and @TheSavior who reviewed it
@grabbou also offered to review on Discord :)

Regarding the changelog – I omitted one because this is because a refactor, and should be a no-op on its own. Can add one if people think it's necessary.

Huxpro

Right now react-native always passes in a config when it calls hermes::makeHermesRuntime. We should update it so it doesn't pass in a config unless there is a custom one being specified. That way, Hermes will be able to determine a default config on its own.

I see where you were coming from, but I don't see this to be particularly useful because:

the runtimeConfig is already an optional parameter so HermesExecutorFactory is effectively overloaded as what you changed to.
the runtimeConfig is already default constructed for the case of 2-params overloads so it's effectively the same as deferring it to the hermes.h.
the use of folly::Optional doesn't make anything safer.

While iOS does not bother specifying a custom config currently, Android does. If we want both platforms to defer to Hermes for the default config, we should remove the custom Android config.

How do you feel about we repurpose this PR to just remove the custom Android config? The Hermes default config change should be committed soon.

EDIT: facebook/hermes@5f2b47d is commited.

Ashoat · 2021-08-09T00:02:30Z

Ah, I see what you mean... makesHermesRuntime's default constructor gets a default-initialized RuntimeConfig anyways. This PR (as it stands) was built on the premise that these are different:

hermes::makeHermesRuntime(::hermes::vm::RuntimeConfig());
hermes::makeHermesRuntime();

But I guess that's not the case. If there's no plan to differentiate these, then I can do as you suggest and make this PR just about reverting the custom Android config.

Summary: The default max heap size GC config of Hermes, 512MiB, is too small to be the default config for React Native apps from the nowadays standard. It casued memory issues on Android (#295) and was mediated by manually [overriding this number to 1024MiB from the RN Android code path](facebook/react-native@63d20d3), and a similar OOM issue was reported on iOS recently (#551). As Hermes being adopted by more platforms (Windows, macOS), it make no sense to override this number again and again in each platforms. Rather, the default max heap should be changed once and for all, The RN side of change is tracked at facebook/react-native#31900. We choose 3GiB which is "unlimited" in practice, making Hermes closer to JSC which doesn't have such limit as well. Reviewed By: neildhar Differential Revision: D30181817 fbshipit-source-id: 54a442e43b7884a9f5d7ed099cb9b9866ee4f109

Huxpro · 2021-08-26T20:59:00Z

@Ashoat I've updated the Hermes default GCConfig a while ago. Let me know when you can get back to this. Ideally we want this making into the upcoming RN 0.66 cut.

Ashoat · 2021-08-27T23:56:54Z

Sorry this has been taking so long! My life has been a bit crazy recently and I haven't been able to find the time.

Looking at this now :)

This reverts commit f8ce862.

Ashoat · 2021-08-28T01:22:10Z

Okay, the PR has been updated!

facebook-github-bot · 2021-08-31T18:12:29Z

@yungsters has imported this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

facebook-github-bot · 2021-09-02T19:31:01Z

@yungsters merged this pull request in a40f973.

yungsters · 2021-09-02T20:17:56Z

Heads up, @Huxpro flagged concerns with this change to me. I just submitted a revert, and he's planning to follow up with more details and proposal for next steps.

facebook-github-bot · 2021-09-02T20:20:20Z

This pull request has been reverted by 455433f.

Huxpro

Thanks @yungsters and @Ashoat !

Regarding the decision of a revert...In a nutshell, I felt like you went too far on removing stuffs that we actually would like to keep.

You removed some critical GCConfig customization (as I highlighted below) which will regress TTI significantly. I'm sorry if my previous wording of "remove the React-Android specific GCConfig in React Native instead" was a little misleading. What I really meant is reverting just the 63d20d3 as you pointed out as "On Android it appears to be overriden to 1024 MiB".

In addition, even if we want to remove all the customized GCConfig, there are way more RuntimeConfig items other than GCConfig so we probably don't want to remove all the RuntimeConfig threading and JNI scaffolding. I understand where you are coming from because GC heapSize happened to be the only POJO field here and rendered them like dead code. However:

It's a moving part that we'll constantly modify whenever we felt the need to expose some Hermes config (e.g. We was using it for Proxy. Who knows what's next?).
A unknown fun fact is that we actually have an internal mirror of this file at FB that exposed way more Hermes config to Java and we'd love to keep the OSS and internal interface consistent.

Due to the tight timeline we have for RN 0.66 (which is already cut and is waiting Hermes for RC2 release), I have to revert it myself at a8ac5ea to make sure things can be cherry-picked on time.

Big shout out to all the investigation and effort you've made and helped us resolving facebook/hermes#511 and similar issue once and for all!

Huxpro · 2021-09-03T00:17:32Z

ReactAndroid/src/main/java/com/facebook/hermes/reactexecutor/OnLoad.cpp

-          // For the next two arguments: avoid GC before TTI by initializing the
-          // runtime to allocate directly in the old generation, but revert to
-          // normal operation when we reach the (first) TTI point.
-          .withAllocInYoung(false)
-          .withRevertToYGAtTTI(true);


Note that this is a flip of the default GCConfig that we customized to optimize TTI for all React Native apps but not going to work on any other environments (hence not suitable to be the Hermes default).

Ashoat · 2021-09-06T18:57:18Z

No worries – I'm glad to have helped!

facebook-github-bot added the CLA Signed This label is managed by the Facebook bot. Authors need to sign the CLA before a PR can be reviewed. label Jul 25, 2021

Ashoat mentioned this pull request Jul 25, 2021

OOM crash on iOS facebook/hermes#511

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elicwhite added the Needs: React Native Team Attention label Jul 26, 2021

Ashoat changed the title ~~Move default Hermes GC config from ReactAndroid to ReactCommon~~ Defer default Hermes config to Hermes package Aug 6, 2021

Defer default configuration to Hermes

f8ce862

Ashoat added the Contributor A React Native contributor. label Aug 8, 2021

Ashoat force-pushed the ashoat/hermes_gc_config branch from 86773fc to f8ce862 Compare August 8, 2021 15:35

Ashoat requested review from Huxpro, alloy and elicwhite August 8, 2021 19:02

Huxpro suggested changes Aug 8, 2021

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facebook-github-bot added the Shared with Meta Applied via automation to indicate that an Issue or Pull Request has been shared with the team. label Aug 12, 2021

Ashoat added 2 commits August 27, 2021 16:58

Revert "Defer default configuration to Hermes"

5a2bab4

This reverts commit f8ce862.

[ReactAndroid] Remove custom Hermes config

0fdf5fe

Ashoat changed the title ~~Defer default Hermes config to Hermes package~~ Remove custom Hermes config for Android Aug 28, 2021

facebook-github-bot closed this in a40f973 Sep 2, 2021

facebook-github-bot added the Merged This PR has been merged. label Sep 2, 2021

facebook-github-bot added the Reverted label Sep 2, 2021

Huxpro reviewed Sep 3, 2021

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Ashoat deleted the ashoat/hermes_gc_config branch September 6, 2021 18:57

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Remove custom Hermes config for Android #31900

Remove custom Hermes config for Android #31900

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Remove custom Hermes config for Android #31900

Remove custom Hermes config for Android #31900

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