Increase memory limits for IcedTea

[Andrew Haley]

Peter B. Kessler writes:
 > Andrew Haley wrote:
 > 
 > > Peter B. Kessler writes:
 > > ....
 > > 
 > >  > 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.
 > 
 > You are probably thinking of reasonable users who want to run in
 > reasonable heaps that leave plenty of address space for other bits
 > of the process.  We get the phone calls from the folks that want
 > to shoehorn the largest possible heap into their address space.
 > Contiguous heaps are pain for them.

Yes, I see.  I suppose I would rather take the position today that
such people really should be using 64-bit systems: AFAIK it has not
been possible to buy a (new) 32-bit x86-based machine for a year or
so.  So, while I accept your point, it's more of an issue for legacy
hardware.  (I'm only considering desktop systems and servers here:
embedded Java is a whole 'nother ball of wax.)

 > The problem is that we don't know in advance if they will want the
 > address space for Java heap, thread stacks, libraries, malloc space,
 > etc.  Otherwise we'd just reserve the whole address space for the
 > heap.  That wouldn't leave any room for anything else, though.
 > It would be better to only reserve the space we need, do the work
 > to make the heap not need contiguous addresses, and make it all work
 > efficiently in the kernel.

I take your point.  I suppose the key question is just how much extra
work in userland can be justified for this effort.

 > (We talk to the kernel engineers for our favorite operating system,
 > too. :-)

(Oh, OK.  :-)

Andrew.

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