How to log the memory consumption on Linux?

Is there any ready-to-use solution to log the memory consumption from the start of the system? I'd like to log the data to simple text file or some database so I can analyze it later.

I'm working on Linux 2.4-based embedded system. I need to debug the problem related to memory consumption. My application automatically start on every system start. I need the way to get the data with timestamps from regular intervals (as often as possible), so I can track down problem.

The symptoms of my problem: when system starts it launched my main application and GUI to visualize the main parameters of the system. GUI based on GTK+ (X server). If I disable GUI and X server then my application works OK. If I enable GUI and X server it does not work when I have 256 MiB or 512 MiB of physical memory installed on the motherboard. If I have 1 GiB of memory installed then everything is OK.

The following script prints time stamps and a header.

#!/bin/bash -e

echo "      date     time $(free -m | grep total | sed -E 's/^    (.*)/\1/g')"
while true; do
    echo "$(date '+%Y-%m-%d %H:%M:%S') $(free -m | grep Mem: | sed 's/Mem://g')"
    sleep 1
done

The output looks like this (tested on Ubuntu 15.04, 64-bit).

      date     time          total       used       free     shared    buffers     cached
2015-08-01 13:57:27          24002      13283      10718        522        693       2308
2015-08-01 13:57:28          24002      13321      10680        522        693       2308
2015-08-01 13:57:29          24002      13355      10646        522        693       2308
2015-08-01 13:57:30          24002      13353      10648        522        693       2308

A small script like

rm memory.log
while true; do free >> memory.log; sleep 1; done

I am a big fan of logging everything and I find it useful to know which processes are using the memory and how much each process is using (as well as sumary statistics). The following command records a top printout ordered by memory consumption every 0.5 seconds:

top -bd0.5 -o +%MEM > memory.log

Just note that the log file will grow a lot faster than if you only store the total memory utilization statistics so be sure you don't run out of disk space.

There's a program called

sar

on *nix systems. You could try to use that to monitor memory usage. It takes measurements at regular intervals. Do a

man sar

for more details. I think the option is -r for taking memory measurements, -i to specify the interval you'd like.

I think adding a crontab entry will be enough

*/5 *  *  *  *  free -m >> some_output_file

There are other tools like SeaLion, New Relic, Server Density etc which will almost do the same but are much easier to install and configure. My favorite is SeaLion, as it being free and also it gives a awesome timeline view of raw outputs of common linux commands.

You could put something like

vmstat X >> mylogfile

into a startup script. Since your application is already in startup you could just add this line to the end of the initialization script your application is already using. (where X is # of seconds between log messages)

To periodically log the memory usage efficiently, I combined another answer here with a method to only retain the top-K memory-using processes.

top -bd 1.5 -o +%MEM | grep "load average" -A 9 > memory_usage.log

This command will record, every 1.5s, the top header information and the 3 highest memory-consuming processes (there's a 6-line offset for top's header information). This saves lots of disk space over recording top's information for every process.

So I know that I am late to this game, but I just came up with this answer, as I needed to do this, and really didn't want the extra fields that vmstat, free, etc... all will seem to output without excess filtering. So here is the answer that I came up with:

top -bd 0.1 | grep 'KiB Mem' | cut -d' ' -f10 > memory.txt

OR:

top -bd 0.1 | grep 'KiB Mem' | cut -d' ' -f10 | tee memory.txt

the standard output from top when grep ing with Kib Mem is:

KiB Mem : 16047368 total,  8708172 free,  6015720 used,  1323476 buff/cache

By running this through cut, we filter down to literally just the number prior to used

The user can indeed modify the 0.1 to another number in order to run different capture sample rates. In my case I wanted to use top also because you can run memory stats faster than 1 second per capture, as you can see here I wanted to capture a stat every 1/10th of a second.

NOTES: It does turn out that piping through cut cause MASSIVE delay in getting anything out to file. As we later found out, it is much faster to leave out the cut command during data acquisition, then perform the cut command on the output file later. Also, we had no need for timestamps in our tests.

This thus looks as follows:

Begin Logging:

top -bd 0.1 | grep 'KiB Mem' | tee memory_raw.txt

Exit Logging:

ctrl-z (to exit logging)

Filter:

2 levels of cut (filtering), first by comma, then by space. This is due to the alignment of top and provides much cleaner output:

cut memory_raw -d',' -f3 | tee memory_used_withlabel.txt
cut memory_used_withlabel.txt -d' ' -f3 | tee memory_used.txt