this post was submitted on 12 Aug 2023
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Possible explanation for jank in Android as opposed to iOS (20 millisecond core ramp on ARM/Android vs 50 microseconds on Apple/iOS) (social.treehouse.systems)
submitted 10 months ago* (last edited 10 months ago) by octalfudge to c/apple_enthusiast
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More useful context:

https://social.treehouse.systems/@chadmed/110874563649736382

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[–] Sheltac 36 points 10 months ago (2 children)

Interesting, I always thought it had to do with Android’s ungodly software stack which at some point involves, of all things, fucking java.

[–] [email protected] -2 points 10 months ago (3 children)

Android doesn’t use Java at a byte-code level and never has, as far as I can tell. Source code was written in Java since mobile developers were so used to it but Android never ran the JVM, they do their own thing with Java source.

You can dislike Java syntax but the software stack on Android wasn’t Java’s.

[–] Sheltac 21 points 10 months ago (2 children)

Wait, thats is very different from what I read back in the day. I know there was a point at, I dunno, android 5 where they started doing something different with java, but my impression was that android always ran a JVM of sorts. And frankly, given how it performs even on the highest-end devices, that was really easy to believe.

I guess I need to do some research now.

[–] bluefirex 36 points 10 months ago (1 children)

No you're correct. Android does run a JVM, just not Oracle's. That has always been the case. Back in the day it was Dalvik, nowadays it's ART.

[–] Sheltac 9 points 10 months ago

There you go, that’s exactly what I was thinking. Thanks!

[–] [email protected] 8 points 10 months ago (1 children)

Pretty sure it was Dalvik virtual machine that Java was compiled to byte code for before 4.4 when they deprecated Dalvik for Android Runtime (ART), fully dropping Dalvik in 5.

[–] [email protected] 7 points 10 months ago (1 children)

@fartsparkles @Sheltac Android always ran dalvik bytecode and never Java bytecode
The change to Art was just a replacement of the "VM", but didn't change what byte code was run. It's similar to how Hotspot improved the Java VM while also not fundamentally changing that it's running Java bytecode.

[–] [email protected] 1 points 10 months ago

Thank you for the insight!

[–] [email protected] 10 points 10 months ago

Dalvik/ART is essentially the same idea. It uses dalvik byte code, much in the same way the JVM operates.

There’s some complexity (it’s designed to do different things, and the whole Oracle lawsuits added some wrinkles) but it’s not so different as you imply.

[–] [email protected] 2 points 10 months ago

They compile Java Bytecode to Dalvik Bytecode and run that on the Android Runtime which is a tiered JIT compiler.

It still inherits the issues of Java such as the GC, no stack allocated value types, poor cache locality, etc. Although tbf the GC on Android is pretty fucking good these days and doesn't pause the world anymore.