Supporting allocation of Java object heap on NV-DIMMS

[Kharbas, Kishor]

Hello all,

I would like to propose adding a capability in the JVM to allocate object heap on new kinds of heterogeneous memories which are exposed through a file system. This could be achieved by adding a command line option to specify a path in the filesystem which would be used for mmap() system call.

Details:
Linux kernel 4.0 onwards supports DAX mode[1] in Ext4 file system [2] which is designed to support new heterogeneous memory devices such as Intel's 3D XPoint memory [3]. DAX mode removes the need for page cache and provides a direct mapping of process virtual space to storage space.
We would like to add a command line option called "FSDirForHeap" which will - 1) Enable using a file system as backing store for Java object heap 2) Use the provided path to create a temporary file for mmap() system call.

The description of the feature can be found at https://bugs.openjdk.java.net/browse/JDK-8153327
and the webrev is uploaded at http://cr.openjdk.java.net/~vdeshpande/8153327/webrev.00/

References:
[1] https://www.kernel.org/doc/Documentation/filesystems/dax.txt
[2] https://www.kernel.org/doc/Documentation/filesystems/ext4.txt
[3] https://newsroom.intel.com/press-kits/introducing-intel-optane-technology-bringing-3d-xpoint-memory-to-storage-and-memory-products/

Much appreciated!
Thanks you.
Kishor Kharbas





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