Log memory of a process

analyze-memlog.py

# Prints the time the log spans and how many bytes per second its memory has increased
import sys
logname = sys.argv[1]
with open(logname) as f:
    first, *_, last = f
    t0, m0  = map(int, first.split());
    t1, m1  = map(int, last.split());
    print(f'Time: [{(t1 - t0)/60:.2f}] at {((m1 - m0)/(t1 - t0)):.2f} B/s')

example-log

1636570520 12796
1636570521 12796
1636570522 13060
1636570523 13060
1636570525 13060
1636570526 13060
1636570527 13060
1636570528 13060
1636570529 13060

memory-log.sh

#logs to a file with format
# seconds-since-epoch memory-used
# you can monitor the file with `tail -f $LOG` from another shell

LOG=log-name
CMDNAME=command-name
rm -f $LOG

while true; do                                                                                                                                         
mem=$(ps -C $CMDNAME --no-headers -o rss) && echo "$(date +%s) $mem" >> $LOG                                                                                                                                                                  
sleep 1
# uncomment to print memory usage live
# python analyze-memlog.py $LOG 
done