how to programmatically monitor a process memory usage?

[thanhvn]

I need to obtain the memory usage (real and virtual) of a particular process every couple of seconds and write it to a log file. I'm thinking of writing either shell script (sh or bash) or a C/C++ program. What shell commands and/or C/C++ API's are available for this task?

Thanks,

[Cabhan]

You might want to take a look at the

ps aux

command for determining process memory usage.

Personally, I'd probably use a regular expression to match the line corresponding to the program and grab out the memory usage, then simply print that to the log file. You could set it to run as a cron job at whatever interval you need it.

[thanhvn]

I am wondering:

1) how to get this GetMemUsage script and the program it monitors to start up at the same time? I don't want to start up the program then open a second console (the program writes to stdout) to launch the script. This means I would miss the first second or two of the program.

2) how to get this GetMemUsage script to shut down cleanly and automatically when the program it monitors shutdowns, even it shuts down abnormally? I would like the ability to batch run the program several times.

Thanks,

[thanhvn]

Also, how to get the elapsed time since the program started (preferrably in milliseconds or better resolution)? other than saving the start time and subtract it from the current time? what if I wanted CPU time and not wall-clock time?

Thanks,

[zOrK]

are u tried with top?

top

regards.

[thanhvn]

zOrk, top is interactive; i don't want interactive, i want a script/program that is:
a) launched automatically when the monitored process is launched,
b) obtain the elapsed time and mem usage, log it to a file, (as efficiently as possible; i don't want this script to have anything other than a negligible effect on the monitored process's performance)
c) goes to sleep for x seconds
d) wakes up and do steps b & c again
e) cleanly and automatically shutdown/exit when the monitored process is shutdown/exit (even if it is exited abnormally or interrupted with Ctrl-C)
any ideas? anyone?

[skrye]

Have you attempted to script this yourself? If so, let us have a look at how far you have got them maybe we could help from there. As i am loath to do your admin work from scratch without anything other from you than your requirements.

[thanhvn]

Fair enough. Here's what I've got so far. This is the GetMemUsage script:

#!/bin/sh

USAGE="Usage: $0 processName"

if [ $# -ne 1 ]; then
   echo $USAGE
   exit 1
fi

# In case the monitored process has not yet started
# keep searching until its PID is found
PROCESS_PID=""
while :        
do
   PROCESS_PID=`/sbin/pidof $1`

   if [ "$PROCESS_PID.X" != ".X" ]; then
      break
   fi
done

LOG_FILE="memusage.csv"

echo "ElapsedTime,VmSize,VmRSS" > $LOG_FILE

ELAPSED_TIME=0
PERIOD=2        # seconds

# Monitor memory usage forever until script is killed
while :        
do
   VM_SIZE=`awk '/VmSize/ &#123;print $2&#125;' < /proc/$PROCESS_PID/status`
   if &#91; "$VM_SIZE.X" = ".X" &#93;; then
      continue
   fi
   VM_RSS=`awk '/VmRSS/ &#123;print $2&#125;' < /proc/$PROCESS_PID/status`
   if &#91; "$VM_RSS.X" = ".X" &#93;; then
      continue
   fi
   echo "$ELAPSED_TIME,$VM_SIZE,$VM_RSS" >> $LOG_FILE
   sleep $PERIOD
   VM_SIZE=""
   VM_RSS=""
   # Needs to get actual elapsed time instead of doing this
   ELAPSED_TIME=`expr $ELAPSED_TIME + $PERIOD`
done

Anyone knows how to get the actual elapsed time of a process (preferrably in milliseconds resolution but seconds resolution is fine)?

I cannot think of any way to have the GetMemUsage script launches and shuts down in synchronization with the monitored process other than to have a launch script that launches and shuts down both processes. Here's the launch script:

#!/bin/sh

Cleanup() {
   kill -9 `/sbin/pidof hello.out`
   kill -9 `ps ux | awk '/GetMemUsage.sh/ {print $2}'`
   exit $1
}
trap 'Cleanup 1' 1 2 3 15
./GetMemUsage.sh hello.out 2>&1 > /dev/null &
./hello.out
Cleanup 0

I realized this is not the most elegant way of doing it. Any suggestions for improvements are more than welcome.

[skrye]

Cool, I shall have a go at it this weekend.

[skrye]

I like the thinking behind this script, I've decided to have a go at re-writing it (maybe in perl) and making it a little more robust because its somthing I myself will find usful i think.

In the interim however i've found a solution to your time issue i think. Its a little basic, and only meant to be a tempory solution but here it is:

#!/bin/sh
#GetmemUsageModified

USAGE="Usage: $0 processName"

if [ $# -ne 1 ]; then
   echo $USAGE
   exit 1
fi

# In case the monitored process has not yet started
# keep searching until its PID is found
PROCESS_PID=""
while :
do
   PROCESS_PID=`/sbin/pidof $1`

   if [ "$PROCESS_PID.X" != ".X" ]; then
      break
   fi
done

LOG_FILE="memusage.csv"

echo "ElapsedTime,VmSize,VmRSS" > $LOG_FILE

ELAPSED_TIME=`date`
PERIOD=2        # seconds

# Monitor memory usage forever until script is killed
while :
do
   VM_SIZE=`awk '/VmSize/ &#123;print $2&#125;' < /proc/$PROCESS_PID/status`
   if &#91; "$VM_SIZE.X" = ".X" &#93;; then
      continue
   fi
   VM_RSS=`awk '/VmRSS/ &#123;print $2&#125;' < /proc/$PROCESS_PID/status`
   if &#91; "$VM_RSS.X" = ".X" &#93;; then
      continue
   fi
   echo "$ELAPSED_TIME,$VM_SIZE,$VM_RSS" >> $LOG_FILE
   sleep $PERIOD
   VM_SIZE=""
   VM_RSS=""
   ELAPSED_TIME=`date +%H&#58;%M&#58;%S&#58;%N`
done

As you can see this is a pretty minimal and basic hack, hopefully it will fill your needs untill my attempt at a re-code. :P Oh and i'm working on the shutdown issue, hopefully when i'm finished it will run as a deamon, shutdown at process death, write to a new log each time ( currently as you probably know it overwrites the last log ) and maybe be able to track more than one process.