In defense of the Windows x86-32 Port

[Thomas Stüfe]

On Sun, Feb 26, 2023 at 6:09 AM <mark.yagnatinsky at barclays.com> wrote:

> I saw this JEP draft today: https://openjdk.org/jeps/8303167.  It
> suggests deprecating the 32-bit Windows port of OpenJDK.
>
> And even though it’s “just a draft” it does mention Java 21 (which is
> pretty soon), so I thought I might as well put in my “two cents” now
> instead of waiting to see whether or not this ends up going anywhere.
>
> The draft is written as though the (primary?) purpose of the port is to
> support running Java on 32-bit versions of Windows.
>
> Those are indeed very rare, and getting even rarer.  But I appreciate the
> 32-bit builds even though I haven’t run a 32-bit version of Windows in ages.
>
> Unlike MacOS, it is possible (and effortless) to run 32-bit executables on
> 64-bit Windows.  There are at least 2 reasons to do so:
>
> The obvious reason is that maybe someone has some native code they’re
> calling via JNI, and they don’t have a 64-bit version handy.
>
> The other reason is perhaps less obvious, and perhaps I’m the only person
> in the world who considers this a “reason” at all, but it motivated me to
> write this email so here it is:
>
> The restriction to 32-bits is pretty effective as a poor man’s substitute
> for a proper sandbox.
>
> For example, the draft JEP talks about Project loom, a topic near and dear
> to me.  When I first heard of Project loom, I wanted to run two silly
> experiments.
>
> The first experiment was to launch as many “platform” threads as I could,
> and thus get a feel for how much they “cost”.  The second experiment was to
> do the same for “virtual” threads.
>
> I actually carried out the first experiment, on a 32-bit JVM.  I did not
> dare to try the same experiment on a 64-bit JVM.
>
> The reason is that I knew that with a 32-bit JVM, I would run out of
> address space before anything bad happened.
>
> But if I tried the same thing with a 64-bit JVM, then for all I know I
> might bring my poor laptop to its knees and might even be forced to restart.
>
> I’ve been eagerly awaiting Alexey Shipilev’s 32-bit port (is anyone else
> besides him working on this?) ever since then so I could try the “loom”
> part of the experiment.
>
> I’ll be a bit disappointed if it never appears.
>
>
>
> Anyway, that’s my two cents; thanks if you read this far.
>

I agree that the JEP description is misleading; as you wrote, Windows 11 is
able to run 32-bit processes.

Note that another advantage of 32-bit ports is that they can save quite a
bit of memory if footprint is dominated by native memory and not java heap.
That may not matter so much for Windows though.

Cheers, Thomas
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