I have atop logs stored on a dayly basis with 10 min interval and I can read them with atop -r <path_to_log>, but how can I find a peak memory usage in this log?
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1 Answer
The command to analyze the recorded data is atopsar.
For example:
# atopsar -r /var/log/atop/atop_20170511 -m -R 1 | head
trucka 3.4.113-sun7i+ #1 SMP PREEMPT Fri Oct 28 16:54:21 CEST 2016 armv7l 2017/05/11
-------------------------- analysis date: 2017/05/11 --------------------------
00:00:01 memtotal memfree buffers cached dirty slabmem swptotal swpfree _mem_
00:10:01 1888M 604M 381M 422M 0M 185M 2047M 2047M
00:20:01 1888M 604M 381M 422M 0M 185M 2047M 2047M
00:30:01 1888M 604M 381M 422M 0M 185M 2047M 2047M
00:40:01 1888M 604M 381M 422M 0M 185M 2047M 2047M
You have to consider what memory is important for you in your case.
It may make sense for you to sort by the third column (memfree) to find the lowest point of free memory. You could also consider to have a look at the swapfree (9th column) to find the point where most memory is used, which causes the memory management to page out to swap.
As an example, I sort the output for lowest memory free with the sort command:
# atopsar -r /var/log/atop/atop_20170511 -m -R 1 | sort -b -k 3,3 | head
trucka 3.4.113-sun7i+ #1 SMP PREEMPT Fri Oct 28 16:54:21 CEST 2016 armv7l 2017/05/11
06:40:01 1888M 416M 400M 612M 9M 164M 2047M 2047M
06:30:01 1888M 543M 423M 483M 4M 141M 2047M 2047M
03:10:01 1888M 551M 376M 480M 0M 184M 2047M 2047M
03:20:01 1888M 551M 376M 480M 0M 184M 2047M 2047M
03:30:01 1888M 551M 376M 480M 0M 184M 2047M 2047M
Just to beautify the output, I will ignore sorting the first 7 rows of autosar's header in the following example:
# atopsar -r /var/log/atop/atop_20170511 -m -R 1 | awk 'NR<7{print $0;next}{print $0| "sort -k 3,3"}' | head -11
trucka 3.4.113-sun7i+ #1 SMP PREEMPT Fri Oct 28 16:54:21 CEST 2016 armv7l 2017/05/11
-------------------------- analysis date: 2017/05/11 --------------------------
00:00:01 memtotal memfree buffers cached dirty slabmem swptotal swpfree _mem_
06:40:01 1888M 416M 400M 612M 9M 164M 2047M 2047M
06:30:01 1888M 543M 423M 483M 4M 141M 2047M 2047M
03:10:01 1888M 551M 376M 480M 0M 184M 2047M 2047M
03:20:01 1888M 551M 376M 480M 0M 184M 2047M 2047M
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What if I want just one number (minimum free memory from log)? is it possible with
awk?– mrgloomCommented May 12, 2017 at 8:46 -
Seems it should be:
atopsar -r /var/log/atop/atop_20170512 -m -R 1 | sed 1,6d | awk '{print $3}' | sed 's:M::g' | sed 's:[^0-9]*::g'| awk 'NF' | sort -n | head -n 1– mrgloomCommented May 12, 2017 at 10:20 -
Thats technical correct so far, but you should think about your intentions of finding out lowest "free memory". free memory can also be low, when the system uses memory as cache because the applications do not require the whole memtotal. Also paged out memory to swap could be important for any memory related investigations. Good luck Commented May 12, 2017 at 10:27
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Seems
memfreeis not 'correct', I don't know how it's calculated, but even in days without heavy load on server it shows about only 30% of memory free.– mrgloomCommented May 12, 2017 at 10:31 -
Sounds perfectly fine for me, as linux utilizes memory for buffers and caches until an application requires more memory. try out:
free -mand compare "free memory" with "available memory":daniel@trucka:~$ free -mtotal used free shared buff/cache availableMem: 1888 312 734 17 840 1496Swap: 2047 0 2047As you can see in my example: there is 1496M of memory available, but 840 are currently used for caches (which is fine). Commented May 12, 2017 at 10:41