Re: Ranting about JVM's default memory limits...
Arne Vajh?j wrote:
Virtual memory on all 32 bit systems is 4 GB (on Windows 32 bit
without /3GB only 2 GB is available for apps).
Ah, good point. There are of course physical limits of virtual memory.
You are thinking about the MS usage of the term "virtual memory" - for
reasons unknown to me they use it about page file.
Xmx and RAM has very little to do with each other.
You can use -Xmx1600m on a system with 256 MB of RAM. I may
run a bit slow if you actually use that much mem though !
Not me. I can't set -Xmx2G on my system (32 bit Windows, 64 bit Intel).
So I have to be aware of the limits on each separate platform.
And still why should I be required to upgrade all of my programs just
because (suppose) MS updates their OS to support 4G more virtual memory?
It's silly. The JVM should just use what's available.
(Back in the old days, Intel supported more virtual memory than address
lines by adding a few more "states" to their external bus: S0-S2. Dunno
if that's still available.)
Xmx is only related to the 32/64 bitness of the OS not to amount of
RAM or size of pagefile.
I think there are some interactions which vary from system to system.
See above for 2G not being accepted on my machine. "Write once, test
everywhere." It seems to be rearing it's ugly head for me.
If you upgrade from 1 GB RAM + 2 GB page file to
2 GB RAM + 4 GB page file then you do not need
to change your Xmx - you can use and you can not
get higher than approx. -Xmx1700m on both
configs.
Well it seems to me that 1700M is just a temporary, platform dependent
limitation. What happens when hardware and OS upgrades? There's a lot
of potential MANIFEST files out there, already installed, that have to
be updated. Why push that work onto developers?
I need the JVM to supply Xmx=available system memory for me. That's
the point.
That is a valid wish. You can always send it to SUN.
I was just making sure it was valid before sending Sun an official
gripe-o-gram.