64-bit client VM

[Erik Trimble]

On 6/25/2011 3:05 AM, David Holmes wrote:
> Aekold Helbrass said the following on 06/25/11 19:37:
>> Sorry if this is wrong mailing list to ask that question, but it's the
>> only one that looks suitable by its description...
>
> It's really a hotspot question so I've cc'ed that list.
>
>> README file tells "64-bit client builds are not directly supported". So:
>> 1) What is the reason of this? Does it mean that client vm source code
>> was not adapted to 64-bit systems or just that Sun/Oracle don't want
>> to provide technical support for this?
>
> We don't build it nor test it on a regular basis internally. The code 
> was originally developed for a proprietary product - Sun Java 
> Real-Time System - and was then added to OpenJDK. We don't officially 
> support it.
>
>> 2) How badly unsupported it it? Will it work fine but possibly will
>> have some bugs, will it work fine but not as efficient as 32-bit
>> client, or it will hardly work at all?
>
> I don't know where it stands regarding support for latest Java 7 
> features, but otherwise it should work ok. No idea how to compare 
> performance against 32-bit client.
>
I'd have to re-look, by AFAIK, the 64-bit client VM is fully 
jdk7-compliant. I don't know about support for the G1 Garbage collector, 
but it has the others.  Performance is a complete unknown.

> Build it and see is all I can advise. The Makefiles will need some 
> tweaking to allow this when doing a full JDK build. Otherwise I think 
> you can just do:
>
> cd hotspot/make
> make LP64=1 product1
>
> David Holmes


Please don't take this as gospel, and I certainly don't speak for Oracle 
in any way, but as the proliferation of 64-bit client OSes increases 
drastically, I would expect that the community will want a 64-bit client 
VM much sooner than otherwise anticipated.

Of course, most OSes will continue to support running 32-bit binaries on 
a fully 64-bit system, but I expect many of the "purists" out there will 
be very interested in getting the client VM fully on 64-bit.

If, for no other reason, than to run with 64-bit Firefox on Linux. <grin>


Also, it might actually simplify Oracle's support in some ways - in 
particular, if we had a 64-bit client VM for Solaris, we could (and 
likely would) completely dump the 32-bit JDK/JRE on Solaris.  Once 
again, that is speculation, but I also can see it happening quite easily.

If someone wants to work on 64-bit client, I certainly don't see anyone 
discouraging it.

-- 
Erik Trimble
Java Platform Group Infrastructure
Mailstop:  usca22-317
Phone:  x17195
Santa Clara, CA
Timezone: US/Pacific (UTC-0800)