Do we really still need a 32-bit JVM?

http://www.kubrynski.com/2015/05/do-we-really-still-need-32-bit-jvm.html

by theredviper • 11 years ago

43 41 11 years ago

So going to 32-bit JVM you sometimes get a slight performance boost, sometimes a slight performance loss, and overall not a huge difference, so I don't think it's really worth it, or even worth trying.

fian• 11 years ago

The performance difference for 32-bit vs 64-bit JVMs can be significant for some workloads. I develop a desktop engineering simulation application in Java.

The simulation time for the same code running the same model on a 64-bit JRE is often almost half the time required on a 32-bit JRE. With simulation times measured in hours to days, this was an extremely nice "freebie" for painlessly migrating to a 64-bit JRE.

We still support 32-bit JREs for each release as many corporate IT departments are still migrating users from 32-bit Windows environments to 64-bit. However, we strongly recommend the 64-bit version for the additional memory space that can be allocated and the reduced simulation time.

gardnr• 11 years ago

As long as there are 32-bit processors or 32-bit hardware accelerated VMs then: Yes.

justincormack2• 11 years ago

Well, 32 bit might get relegated to microcontrollers soon, and other specialist stuff that doesnt run the JVM much. I cant see much mainstream 32 bit hardware being made in even 5 years.

copsarebastards5• 11 years ago

I'm not sure where you're getting your information here. One very pervasive area I don't see going 64-bit any time soon is cable settop boxes.

cwyers2• 11 years ago

That seems like a pretty radical claim, considering that something like 99.9% of extant Android phones are 32 bit.

pjmlp2• 11 years ago

It doesn't run Oracle's JVM, but there are plenty of other ones to choose from.

nayuki2• 11 years ago

Even today there are some minority 32-bit products around in the PC world where the Oracle Java VM can run.

For example the HP Stream 7 tablet runs Windows 8.1 32-bit edition on x86 Intel Atom Z3735G (CPU is x86-64 capable). It can only support the 32-bit JVM.

copsarebastards5• 11 years ago

This is the only answer.

Java is intended to be right once, run anywhere. "Anywhere" will include 32 bit address spaces for the forseeable future.

hobo_mark• 11 years ago

That is a lovely typo.

MichaelGG2• 11 years ago

64 bit JVM can target 32-bit address space just fine. In fact if you know you're doing that, then with 4 byte alignment, you only need 30 bits for a pointer, leaving 2 for other optimizations. Maybe.

See also: X32.

pjmlp2• 11 years ago

Not only that, as usual there is the fallacy that there is only one JVM.

Here are a few 32 bit ones for the embedded market:

http://www.is2t.com/products/

https://www.aicas.com/cms/en/JamaicaVM

http://www.atego.com/products/atego-perc-pico/

Gibbon1• 11 years ago

So meaning, oh yes please drop support for 32bit, please!!!!

protomyth• 11 years ago

How is time handled on a 32-bit JVM?

newobj• 11 years ago

32-bit is with respect to addressable memory. All JVMs still have 64 bit longs and doubles, etc.

organsnyder• 11 years ago

Java has always stored time values as 64-bit longs representing milliseconds since the Unix epoch. This includes System.currentTimeMillis(), as well as what the java.util.Date class uses internally. I'm assuming that the Java 8 date-time API also does this (or something better—either way, I'm certain that it's y2038-compliant).

So, even 32-bit Java is good for another 292 million years or so.

manishsharan• 11 years ago

Garbage collection is much faster on 32 bit JVM than a corresponding 64 bit JVM. Therefore I prefer to my small web applications or component that don't need a ton of heapspace on 32 bit JVM.

m0th87• 11 years ago

Can't you tune a 64-bit JVM to have a smaller heap or GC as aggressively as a 32-bit JVM?

MrBuddyCasino2• 11 years ago

Citation needed. Is this true even with compressed pointers?

breischl• 11 years ago

Um, the article explicitly tested that case. Does that count as a citation?

peapicker• 11 years ago

Another consideration is that many shops have in place C and C++ code that is 32 bit, which hosts JVMs and uses JNI to talk to them.

lbearl• 11 years ago

Yep, and that code isn't going anywhere anytime soon. Big, boring, slow moving enterprise software. I work on one of these systems.

nikanj• 11 years ago

Maybe you don't, but we most definitely do.

ww520• 11 years ago

Yes. 32-bit machines are going away any time soon.

nayuki2• 11 years ago

Did you mean to write "aren't"?

ci5er• 11 years ago

Short answer: Yes

Longer answer: Why would you assume that your development preferences (yes, preferences! not needs!) are so important as to justify cutting the legs out from underneath a huge swath of problems that other people on the planet are working on?

rilita• 11 years ago

Article more or less: "I don't think that we do, so I tested it a bit. Tests confirm my assumptions. Still; there are cases where 32 bit is faster. I won't bother to explain why."

As usual "All headlines that ask a question can be answered no" ( but inverted to make it more confusing ). Really the title of the article to fit the mold should be "Can we get rid of the 32-bit JVM?"

Really what should be done is take the algorithms from language competition website, and then test all of those on 32-bit versus 64-bit with different data sets. A few tests is hardly conclusive or explanative of what is fast and what is slow.

Obviously a raw call to nanotime will be slow. Do you really need nanotime? If you don't; is a lower precision call faster than nanotime?

Do we really still need a 32-bit JVM?

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