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I have computer handling various functions for our community radio station, including processing the program audio for broadcast. It's running remotely and sends daily health emails for me to keep an eye on its status. I am seeing free memory drop - by quite a lot - over the course of a few days and can't account where it is going.

The report contains the output of "free" and the top 20 processes using memory:

ps -eo comm:15,pid,ppid,cmd,%mem,%cpu --sort=-%mem | head -n 20

Two days ago:

Memory stats as of 10/17/2023
               total        used        free      shared  buff/cache   available
Mem:            12Gi       3.1Gi       7.4Gi       160Mi       2.1Gi       9.0Gi
Swap:             0B          0B          0B
Total:          12Gi       3.1Gi       7.4Gi

MEM stats
COMMAND             PID    PPID CMD                         %MEM %CPU
ST_FM              2214       1 /home/kpov_tech/Desktop/Ste  4.6 24.1
ST_Stream          2256       1 /home/kpov_tech/Desktop/Ste  4.5 21.6
plasmashell        1759    1689 /usr/bin/plasmashell         2.0  0.2
kwin_x11           1721    1689 /usr/bin/kwin_x11            1.8 10.7
fluidsynth         1538    1528 /usr/bin/fluidsynth -is /us  1.8  0.0
kded5              1718    1689 /usr/bin/kded5               1.8  0.0
audacious        871581  827042 /usr/bin/audacious --play    1.6  1.6
Xorg               1259    1218 /usr/lib/xorg/Xorg -noliste  1.3 16.8
dolphin          774584    1759 /usr/bin/dolphin             1.2  0.1
kwrite            44322       1 /usr/bin/kwrite /home/kpov_  1.1  0.1
konsole            2097       1 konsole --noclose --profile  1.0  0.1
raysession         2307       1 /usr/bin/python3 -u /usr/sh  1.0  0.3
jackd              2111    2097 /usr/bin/jackd -v -d alsa -  1.0  0.7
zita-mu1           2173       1 /usr/bin/zita-mu1 -name MON  0.9  0.4
ebumeter           2191       1 ebumeter -name ebu_Raw_MCR   0.9  1.0
ebumeter           2207       1 ebumeter -name ebu_ListenLi  0.9  0.9
ebumeter           2200       1 ebumeter -name ebu_ST_FM     0.9  0.9
ebumeter           2184       1 ebumeter -name ebu_ST_Strea  0.9  0.9
ray-jackpatch_t    2330       1 /usr/bin/python3 -u /usr/sh  0.9  0.1

Today:

Memory stats as of 10/19/2023
               total        used        free      shared  buff/cache   available
Mem:            12Gi       3.8Gi       529Mi       155Mi       8.2Gi       8.2Gi
Swap:             0B          0B          0B
Total:          12Gi       3.8Gi       529Mi

MEM stats
COMMAND             PID    PPID CMD                         %MEM %CPU
ST_FM              2214       1 /home/kpov_tech/Desktop/Ste  4.6 24.1
ST_Stream          2256       1 /home/kpov_tech/Desktop/Ste  4.5 21.8
plasmashell        1759    1689 /usr/bin/plasmashell         2.4  0.2
fluidsynth         1538    1528 /usr/bin/fluidsynth -is /us  1.8  0.0
kwin_x11           1721    1689 /usr/bin/kwin_x11            1.8  9.5
audacious        871581  827042 /usr/bin/audacious --play    1.5  1.6
Xorg               1259    1218 /usr/lib/xorg/Xorg -noliste  1.2 16.4
dolphin         3467064    1759 /usr/bin/dolphin             1.1  0.1
kwrite            44322       1 /usr/bin/kwrite /home/kpov_  1.0  0.1
kded5              1718    1689 /usr/bin/kded5               1.0  0.0
jackd              2111    2097 /usr/bin/jackd -v -d alsa -  1.0  0.7
konsole            2097       1 konsole --noclose --profile  1.0  0.0
raysession         2307       1 /usr/bin/python3 -u /usr/sh  1.0  0.3
xdg-desktop-por 3450540    1528 /usr/lib/x86_64-linux-gnu/l  0.9  0.0
zita-mu1           2173       1 /usr/bin/zita-mu1 -name MON  0.9  0.4
ebumeter           2191       1 ebumeter -name ebu_Raw_MCR   0.9  1.0
ebumeter           2207       1 ebumeter -name ebu_ListenLi  0.9  0.9
ebumeter           2200       1 ebumeter -name ebu_ST_FM     0.9  0.9
ebumeter           2184       1 ebumeter -name ebu_ST_Strea  0.9  0.9

It looks to me that something like 7Gi of Free memory has evaporated. How can I find out what is using it?

Artur Meinild
  • 31,035
thatjackelliott
  • 145

1 Answers1

6

From the output of the "free" application it is apparent that you have approximately 8-9Gi of memory available.

What might be confusing to you is that under the column labeled "free" you see a very small amount of memory - this is normal behavior.

You have to factor into your available memory the amount under the "buff/cache" column - Linux uses available memory as buffers to help speed up other processes when possible, and this memory is not unavailable in a traditional sense - you can still use it for other applications if you need to.

You can see the total available memory on your system listed under the "available" column in your logs.

kishkovert
  • 167