Increase memory limits for IcedTea

[Andrew Haley]

Peter B. Kessler writes:
 > You could do something ergonomic like looking to see how much
 > memory the machine has, and guessing what kinds of applications
 > will be run on it that way.  But basically you are guessing
 > what the application needs before it starts running, which isn't
 > a good way to go.

Agreed.  It's not a matter of whether or not we have to guess: the
architecture of the VM is such that we are forced to to pick a default
limit, so it's a matter of choosing the right one.

 > I sometimes wish we had the luxury of knowing what kinds of
 > applications a particular installation will run, rather than having
 > to balance the needs of applets in browsers and servers running
 > applications with 32GB heaps.
 > 
 > Note that the maximum space sizes only reserve memory, they
 > don't commit it, so you are just tying up address space and
 > swap space, not memory, if you don't actually grow into that
 > space.

Absolutely: on GNU/Linux systems there's no memory wasted until you
touch it, so we suffer almost no hit at all by increasing the default
so it can accommodate Eclipse et al.

 > The right solution is to make it so the heap doesn't have to
 > be in contiguous memory.  Anyone want to help work on that?

Hmm.  Surely it's better / more efficient to ask the kernel to map a
contiguous range of pages rather than for the VM do more work in user
space.  The nice thing about Java on Linux is that we're in a position
to ask the kernel engineers to help us with what we need.

Andrew.

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