Questions[background-process](ubuntu)

I'm using Ubuntu 20.04 and am working on performance optimisations of some CFD code. When timing my code for quick feedback as to whether some modification is beneficial, there's often quite large run-to-run variance, due to background processes kicking in.

Because the code is using all available threads, any one thread being burdened with background tasks causes all others to wait.

Now my question is, whether or not there is a quick and easy way to temporarily halt background/non-essential tasks and therefore put my system into a kind of benchmark mode. Bash scripts, packages, built-in options, all is welcome.

This morning, running top, I noticed a process I nave never seen before in my Ubuntu 18.04 laptop called MainThread, which was periodically using a lot of CPU . There was also an entry called Privileged Cont.

I recently installed nordvpn, but nordvpn support said the process is not theirs. Is this a new part of the operating system? Is it malware? It has never appeared in top on my laptop before, as far as I know.

I'm trying to understand what the different background processes are doing on my machine as this one is freezing from time to time. I have noticed that the tracker processes (there are several of them as you can see on the screenshots) take a lot of CPU power. I also noticed that if I kill those processes, it solves the issue and nothing weird or at least nothing visible really happen on my machine.

Do you know what is exactly the use of those processes and why they are taking so much CPU power (what are they doing with all that power?) I tried to do a couple of searches online regarding the tracker processes but I can't really understand what they do. :/

Thanks in advance for you answer, I'm really eager to learn more about Linux ! :))

screenshot tracker processes :

tracker -store taking a lot of CPU power :

tracker -extract taking a lot of CPU power :

Every time starting the machine, I run the following program:

$ cat start.sh
#! /bin/bash
google-chrome &> /dev/null &
lantern &> /dev/null &
xdg-open . &> /dev/null &
emacs &> /dev/null  &
code ~/Programs/ &> /dev/null &
xdg-open ~/Reference/topic_regex.md &> /dev/null &

Cumbersome &> /dev/null &... How could I shorten the logic?

I have been running below script on a Red Hat server, and it works fine and finishes the job. The file I am feeding it, contains half a million lines in it (approximately 500000 lines), and that's why (to finish it faster) I have added an '&' at the end of while loop block

But now I have setup a Desktop with 8 GB of RAM running Ubuntu 18.04 on it, and running the same code only finishes a few thousand lines and then hangs. I read a bit about it and increased the stack limit to unlimited as well and still it hung after 80000 lines or so, Any suggestions about how can I optimize the code or tune my PC parameters to always finish the job?

while read -r CID60
do    
 { 
       OLT=$(echo "$CID60" | cut -d"|" -f5) 
       ONID=${OLT}:$(echo "$CID60" | cut -d, -f2 | sed 's/ //g ; s/).*|//') 
       echo $ONID,$(echo "$CID60" | cut -d"|" -f3) >> $localpath/CID_$logfile.csv       
  } &     
done < $localpath/$CID7360

Input:

202-00_MSRFKH00OL6:R1.S1.LT7.PON8.ASSN45| Unlocked|12-654-0330|Up|202-00_MSRFKH00OL6|P282018767.C2028 ( network, R1.S1.LT7.PON8.ONT81.SERV1 )|

202-00_MSRFKH00OL6:R1.S1.LT7.PON8.ASSN46| Unlocked|12-654-0330|Down|202-00_MSRFKH00OL6|P282017856.C881 ( local, R1.S1.LT7.PON8.ONT81.C1.P1 )|

202-00_MSRFKH00OL6:R1.S1.LT7.PON8.ASSN52| Unlocked|12-664-1186|Up|202-00_MSRFKH00OL6|P282012623.C2028 ( network, R1.S1.LT7.PON8.ONT75.SERV1 )|

output:

202-00_MSRFKH00OL6:R1.S1.LT7.PON8.ONT81.SERV1,12-654-0330

202-00_MSRFKH00OL6:R1.S1.LT7.PON8.ONT81.C1.P1,12-654-0330

202-00_MSRFKH00OL6:R1.S1.LT7.PON8.ONT75.SERV1,12-664-1186

my output of interest is 5th column ( separated with pipe | ) being concatenated with part of last column, and then the third column