OpenJDK not ready for virtualized environments

[Florian Weimer]

* Jaroslav Tulach:

> After a discussion at #openjdk it looks like like a result of changing the 
> defaults in amount of heap size and perm gen size. I believe the change is 
> wrong. It shall rather check the # of available memory and if lower than 1GB 
> stick with old defaults.

Actually, the correct fix would be to reserve the address space
initially (so that you get one contiguous chunk), and allocate backing
store only as needed.

On Linux, you can do this by specifying PROT_NONE to mmap() and use
mprotect() later. (MAP_NORESERVE is different, and difficult to get
right because the garbage collector must be prepared to deal with
SIGSEGV when the used portion of the heap expands during GC.)

-- 
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