Please implement client switch in 64-bit server JDK 14 builds

[Philip Race]

I think rather than unimplemented, it is actually no longer supported 
and the option is now ignored.

And my recollection could be off, but I thought client VM was mainly or 
maybe only a 32 bit JDK feature
so asking for it on 64 bit may be missing the point on memory consumption.

There would be a non-trivial effort to support it and 32 bit at an OS 
level is getting rarer so
64 bit JDKS are following along.
And I think there is  a trend towards desktop OSes only supporting 64 
bit apps.

So the cost of doing what you asked in both development and testing is 
huge and
the desirability of it can't escape that.

So instead try a 32 bit build and see if that gets you mostly where you 
want to go.

-phil.


On 7/18/19, 7:46 PM, Ty Young wrote:
> Hi,
>
>
> I'm requesting that the long unimplemented "client" java switch be 
> implemented in Java 14.
>
>
> (Note: this entire request is based on the assumption that a JVM with 
> -client is equivalent to a client JVM variant. If this is wrong, I 
> apologies. There isn't much documentation to go on.)
>
>
> Since there aren't many google results or any kind of mention of this 
> feature/ability even existing, i'll give an explanation to the best of 
> my knowledge and personal observations:
>
>
> A "client" JVM variant is geared towards graphical end-user 
> applications. According to a URL link found in the man entry for 
> java[1] this supposedly results in faster startups. While this *may* 
> be true, a much larger and more important benefit is a massive 
> committed memory reduction in the range of about 25% to 50% when 
> running a JavaFX application. At minimum with similar heap sizes, that 
> is a 75 MB memory savings at 300MB (a somewhat typical peak usage with 
> JavaFX applications) with a typical server JVM. That's huge.
>
>
> The downside to this however is that at most, the maximum amount of 
> (committed?) memory that a client JVM variant can use is somewhere 
> around 300MB by default. For the intended purpose of the client JVM 
> switch/variant this is *probably* fine. Server JVM variants only seems 
> to allocate more memory to boost performance, which really isn’t that 
> much of a difference with the intended use case of the client JVM 
> switch/variant… especially considering the more appealing memory savings.
>
>
> So why should this be implemented?
>
>
> The answer is simple: using more memory then is necessary is bad, 
> angers users, and frustrates developers who want to be responsible by 
> not wanting to eat up their users's memory[2] when it isn't needed.
>
>
> Even if you've have never heard anyone complain about Java's memory 
> usage, you've most likely heard someone complain about a similar 
> cross-platform software: Electron. People hate Electron applications 
> for their absurd memory usage and will actively avoid them by using 
> alternatives if possible.
>
>
> For reference, Etcher, an Electron application that allows users to 
> easily create bootable USB drives on Windows, Linux, and probably Mac 
> OS uses around 298 MB just at launch on Linux. Electron is both 
> comparable in both goals(cross-platform solutions, JavaFX vs. 
> Electron) and in memory usage.
>
>
> Java may not be a native language and there may be *some* unavoidable 
> penalty for that but being wasteful and consuming resources where not 
> necessary is, well, unnecessary. This can help reduce the amount of 
> memory a java application uses significantly when used.
>
>
> With that all said, since JEPs include risks/impact/problems, it's 
> best to mention some that come to mind:
>
>
> Because of the default lower memory limit, applications which go 
> beyond this will fail. The easiest and best workaround would be to 
> simply make the client JVM switch/variant opt-in. This would allow all 
> existing Java applications to continue to work as expected.
>
>
> The only other issue that I can think of is people launching 
> applications with -client without knowing the limitations of it and 
> filing bogus bug reports to app developers. This can be mitigated with 
> better documentation and awareness in places like the man page for 
> Java. Since no one seems to really have used or knew about it before 
> it's more likely end developers that will be passing the switch to 
> their applications via scripts then end users will be.
>
>
> All in all, this is pretty safe as long as server JVM switch/variant 
> remains the default. Maybe others can think of other 
> risks/impacts/problems.
>
>
> And finally addressing the two questions/comments I imagine someone at 
> some point are going to ask/say:
>
>
> Why not just compile a client JVM variant from source and use jLink?
>
>
> and/or
>
>
> If heap and garbage collection is healthy, who cares?
>
>
> For the first one, yes, this is a route that could be taken. It has 
> some problems however, namely:
>
>
> - You have to be the developer or have source code access to use jLink.
>
>
> - jLink -from my understanding- requires a **fully** modular Java 
> application. Some used libraries may not be modular yet.
>
>
> - A full JDK source code compile is required - something that is 
> really easy to do under Linux but might not be under Windows and takes 
> considerable CPU power to do. No one that I’m aware of (on Linux 
> anyway) provides client JVM variant builds. Presumably This is because 
> the server JVM variant is the most versatile.
>
>
> and as for the second: just because there is say, 5.8GB out of 8GB 
> available doesn't mean you should or have the right to use it as you 
> see fit. People do more than use Java applications. If you are running 
> a web browser with lots of tabs open, a Java application could 
> realistically cause major system stuttering as memory is moved to 
> swap/pagefile. While I used 300MB above as an easy realistic example, 
> i've seen JavaFX applications consume as much as 700MB and even 1GB 
> committed memory. Just opening Scene Builder and playing around with 
> the GUI consumes 400MB easily on a server JVM variant(Oracle JDK/JRE 
> 10 to be exact). While memory usage may never be as good as native, 
> the current amount of memory being consumed is insane and any normal 
> user with standard amount of memory(6-8GB) *will* feel this. Adding 
> this switch could potentially help a lot here and give Java a slight 
> edge over similar software solutions.
>
>
> Can this feature please be implemented? Likewise, could the 
> documentation on what a "client" JVM and other JVM variants be updated 
> and improved?
>
>
> [1] 
> https://docs.oracle.com/javase/8/docs/technotes/guides/vm/server-class.html
>
>
> [2] 
> https://stackoverflow.com/questions/13692206/high-java-memory-usage-even-for-small-programs
>