[concurrency-interest] Default Stack Size on 64-bit JVMs

Martin Buchholz martinrb at google.com
Wed Dec 2 19:12:53 EST 2015


On Wed, Dec 2, 2015 at 9:40 AM, Nathan Reynolds <nathan.reynolds at oracle.com>
wrote:

>
> First, the larger stack size eats up address space.  As far as resources
> go, it is very cheap at this point in time on a 64-bit machine.  25 years
> ago we said the same thing about virtual address space on 32-bit machines.
> We've got about 60 years before we will start exhausting the 64-bit address
> space.  So, let's ignore that for now.  Today's problem comes when doing
> sizing calculations.  People will see the address space size and figure
> that is what is needed for the process in terms of RAM.  Then the entire
> sizing calculation goes haywire and machines end up over sized.  As a cloud
> provider, I don't mind people spending more money on RAM they aren't
> using.  :)
>

The assumption is that the VM implementers can manage to spend _only_
address space.  Maybe mmap with PROT_NONE, maybe madvise(DONT_USE),
whatever it takes to convince the OS (and ps!) that you're not really using
that memory ... yet

... and of course start working on the difficult task of being able to move
the stack so that if you run out of room, simply realloc and move
elsewhere, like the competition is doing.
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