khyox/perm-je

PERsistent heap Management library (LLNL-CASC)

PERsistent heap Management library

Overview

PERM is a 'C' library for persistent heap management and is intended for use with a dynamic-memory allocator (e.g. malloc, free). The PERM memory allocator replaces the standard 'C' dynamic memory allocation functions with compatible versions that provide persistent memory to application programs.

Memory allocated with the PERM allocator will persist between program invocations after a call to a checkpoint function. This function essentially saves the state of the heap and registered global variables to a file which may reside in flash memory or other node local storage.

A few other functions are also provided by the library to manage checkpoint files. Global variables in an application can be marked persistent and be included in a checkpoint by using a compiler attribute defined as PERM. The PERM checkpoint method is not dependent on the programming model and works with distributed memory or shared memory programs.

Method

PERM works closely with the dynamic memory allocator and monitors chunks of memory returned by the operating system and used by the application program. Whole chunks or portions thereof are written to persistent media at checkpoint time.

Platform support

Any 32-bit or 64-bit machine with Linux, FreeBSD, or Mac OS X is supported.

Linux, FreeBSD, Mac OS X (mmap support is required)

Details

Please, read README.PERM for further details.

Tuning the kernel

For PERM to work in the right conditions, some kernel tunning is advisable:

• Turn off periodic flush to file and dirty ratio flush:

echo 0 > /proc/sys/vm/dirty_writeback_centisecs
echo 100 > /proc/sys/vm/dirty_background_ratio
echo 100 > /proc/sys/vm/dirty_ratio

• Turn off address space randomization:

echo 0 > /proc/sys/kernel/randomize_va_space 

References

1. PERM, https://computation.llnl.gov/projects/memory-centric-architectures/perm
2. jemalloc, dynamic memory allocator, https://github.com/jemalloc/jemalloc