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by tgma 378 days ago
Your comment is definitely true. However, if you study GC performance academic papers over the past three for four decades, they pretty much conclude GC overhead, amortized, can be on par with manual alloc/free[1], but usually the unwritten assumption is they have unbounded memory for that to be true. If you study how much memory in practice you need not to suffer a performance loss on an amortized basis, you'd arrive at 2-3x, so I'd claim it is fair to assume Java needs 2-3x as much memory as Swift/C++/Rust to run comfortably.

You can actually witness this to some degree on Android vs iPhone. iPhone comfortably runs with 4GB RAM and Android would be slow as dog.

[1]: I don't dispute the results, but I also like to note that as a researcher in Computer Science in that domain, you were probably looking to prove how great GC is, not the opposite.
1 comments
wiseowise 378 days ago
Android doesn’t even run JVM.

> iPhone comfortably runs with 4GB RAM and Android would be slow as dog.

This has nothing to do with RAM. Without load, Android wouldn’t even push 2GB, it would be still slower than iPhone because of different trade-offs they make in architecture.

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tgma 378 days ago
The point was GC cost in general, not which Java/JVM implementation you choose. Try comparing two Androids with the same chipset at 4GB vs 8GB RAM.

Anyhow, that was just an anecdotal unscientific experiment to give you some idea--obviously they are two different codebases. The literature is there to quantify the matter as I noted.

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pjmlp 378 days ago
Android for a very long time lacked a quality JIT, AOT and GC implementation, and then each device is a snowflake of whatever changes each OEM has done to the device.

Unless one knows exactly what ART version is installed on the device, what build options from AOSP were used on the firmware image, and what is the mainline version deployed via PlayStore (if on Android 12 or later), there are zero conclusions that one can take out of it.

Also iOS applications tend to just die, when there is no more memory to make use of, due to lack of paging and memory fragmentation.

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