[sylware]

linux had a bitmap based "buddy allocator" (power of two), now it is not bitmap based anymore (complexity not worth it anymore, performance wise, namely simplicty was restored).

Then linux has various slabs(slub/slob/slab), built on top of the "buddy allocator".

Userlevel code shoud use non virtual address stable mmap-ed regions (slabs + offsets). Legacy "libc" services were built as virtual address stable services... which are kind of expensive to manage on a modern paginated system. Virtual address stable regions should be kept to a minimum (that horrible ELF static TLS). There is a workaround though (but linux overcommit default policy could kill your process): a user process would query the amount of ram on the system and mmap a region of roughly (care of the overcommit policy) the same size, only once per process life-time. Then you could have a virtual address stable region which could use most if not all the available ram (excluding hot-memory addition...). Should be very easy to manage with lists.

[ogurechny]

In this case, one should start with implementing -Xmx switch, then gradually adding the rest.