Measure selected processes memory usage

For benchmarking experiments I needed a tool that would measure memory usage of specific processes for a period of test run. This could be done in many ways, for example as part of test framework or by using some shell scripts, but I chose to write a small Rust app. The reason was to have universal solution not baked into testing framework, small memory footprint, flexible to satisfy any future needs and obviously to play with Rust.

Usage:

$ agent

Stores processes memory usage in memory and on SIGINT writes log of top 10 processes to stdout.

For example:

$ agent > log.dat
$ ./benchmark-rabbit
benchmark done
$ pkill -2 agent
$ cat agent.log
"ts" "benchmark-rabbit" "beam.smp" "beam.smp" "p4" "p5" "p6" "p7" "p8" "p9" "p10"
27 551 538 398 263 164 164 159 150 146 139
1050 551 538 398 262 164 164 159 150 146 139

Turn agent output into gnuplot diagram:

$ agent > log.dat
$ <EOF > diag.gnuplot
set datafile missing "-"
set term png size 1024,768
set style data linespoints

set key outside
plot for [col=2:*] 'log.dat' using 0:col with lines title columnheader
EOF
$ gnuplot < diag.gnuplot > diagram.png

Sample diagram