Use DAX in ZGC

[Yasumasa Suenaga]

Hi all,

I tried to allocate heap to DAX on Linux with -XX:AllocateHeapAt, but it couldn't.
It seems to allow when filesystem is hugetlbfs or tmpfs.

According to kernel document [1], DAX is supported in ext2, ext4, and xfs.
Also we need to mount it with "-o dax".

I want to use ZGC on DAX, so I want to introduce new option -XX:ZAllowHeapOnFileSystem to allow to use all filesystem as backing storage.
What do you think this change?

   http://cr.openjdk.java.net/~ysuenaga/dax-z/

If it can be accepted, I will file it to JBS and will propose CSR.


Thanks,

Yasumasa


[1] https://www.kernel.org/doc/Documentation/filesystems/dax.txt