FRSS

Introduction

FRSS is a library for printing the resident set size (RSS) of a Fortran application at runtime. It is MPI-aware and displays the memory information for the corresponding MPI rank. It can also be used to measure the maximum values for the occupied memory and GPU device memory (if applicable) on a node.

Usage

Print the RSS of an MPI task

Anywhere in your Fortran code, you can trigger the output by calling the subroutine:

call frss_print()

It will print the following information to stdout:

Abbreviation	Description	Source
RSS	Current resident set size	VmRSS in /proc/self/status
HWM	High water mark of the RSS	VmHWM in /proc/self/status
OOM	Out-of-memory score	/proc/self/oom_score
dt	Elapsed wall-clock time since last call

If you want to display this information only for a specific MPI rank, call (e.g. for rank 0):

call frss_print_rank(0)

Monitor memory of a node

To determine the high water mark of the used memory per node, you need to start the measurement by providing the desired time sampling. For extracting the memory information every 1000 milliseconds, for example, set the following environment variable:

export FRSS_MONITOR_NODE=1000

This will start the measurement automatically and print the result to stdout when the application finishes:

Abbreviation	Description	Source
RAM	Maximum used memory on the node	MemTotal and MemAvailable in /proc/meminfo
GPU	Maximum used GPU device memory on the node	FB Memory Usage in output of nvidia-smi -q -d MEMORY

The RAM value is normalized to an initial offset measured before the application is loaded into memory. This normalization is most accurate if FRSS is the first shared library to be loaded. The GPU value is not normalized in this way.

The printed values may underestimate the actual peak memory usage, because (1) the time sampling may be too coarse or (2) the initial memory usage measured at startup may include previously loaded shared libraries.

Note that a highly resolved time sampling could slow down the application considerably and that meaningful results can only be achieved if the node is used exclusively by your application.

Building

Run make to build the library libfrss.so. The Makefile is prepared to build with Intel Fortran compiler.

Linking

In order to use FRSS, you need to link with the library, e.g. by using the following flags: -L/path/to/frss -lfrss.

License

GPLv3