isabella232 / llpl

Low Level Persistence Library

Low Level Persistence Library

OVERVIEW

The Low Level Persistence Library offers access to persistent memory using MemoryBlocks allocated from a persistent Heap.

This Java library uses the libpmemobj library from the Persistent Memory Development Kit (PMDK). For more information on PMDK, please visit http://pmem.io and https://github.com/pmem/pmdk.

HOW TO BUILD & RUN

PREREQUISITES TO BUILD

The following are the prerequisites for building this Java library:

1. Linux operating system (tested on CentOS 7.2)
2. Persistent Memory Development Kit (PMDK)
3. Java 8 or above
4. Build tools - g++ compiler and make

PREREQUISITES TO RUN

This library assumes the availability of hardware persistent memory or emulated persistent memory. Instructions for creating emulated persistent memory are shown below.

EMULATING PERSISTENT MEMORY

The preferred way is to create an in-memory DAX file system. This requires Linux kernel 4.2 or greater. Please follow the steps at:

http://pmem.io/2016/02/22/pm-emulation.html

Alternatively, for use with older kernels, create a tmpfs partition as follows (as root):

$ mount -t tmpfs -o size=4G tmpfs /mnt/mem  # creates a 4GB tmpfs partition
$ chmod -R a+rw /mnt/mem                    # enables read/write permissions to all users

STEPS TO BUILD AND RUN TESTS

Once all the prerequisites have been satisfied:

$ git clone https://github.com/pmem/llpl.git
$ cd llpl
$ make && make tests

Available Makefile targets include:

• sources - builds only sources
• examples - builds the sources and examples
• tests - builds and runs tests

USING THIS LIBRARY IN EXISTING JAVA APPLICATIONS

To import this library into an existing Java application, include the project's target/classes directory in your Java classpath and the project's target/cppbuild directory in your java.library.path. For example:

$ javac -cp .:<path>/llpl/target/classes <source>
$ java -cp .:<path>/llpl/target/classes -Djava.library.path=<path>/llpl/target/cppbuild <class>

CONTRIBUTING

Thanks for your interest! Right now, substantial architectural changes are still happening in the project. This makes it difficult to contribute code and difficult to effectively process pull requests. We expect these changes to settle out around December of this year and we look forward to code contributions once this happens. We will update this README then.

In the meantime, we would love to hear your comments and suggestions via the contacts listed below.

Contacts

For more information on this library, contact Olasoji Denloye ([email protected]) or Steve Dohrmann ([email protected]).