How is memory used value derived in check_snmp_mem.pl?

Question

I was configuring icinga2 to get memory used information from one linux client using script at check_snmp_mem.pl . Any idea how the memory used is derived in this script ?

Here is free command output

# free
              total        used        free      shared  buff/cache   available
Mem:         500016       59160       89564        3036      351292      408972
Swap:       1048572        4092     1044480

where as the performance data shown in icinga dashboard is

    Label   Value        Max             Warning     Critical
ram_used    137,700.00   500,016.00     470,015.00   490,016.00
swap_used   4,092.00     1,048,572.00   524,286.00   838,858.00

I don't understand the question. You have the source code so you know how it is calculated. — jww, Oct 31 '18 at 10:29
@jww i know nothing about perl language so i posted source code for reference — sherpaurgen, Oct 31 '18 at 11:18

score 0 · Accepted Answer · answered Oct 31 '18 at 13:06

Looking through the source code, it mentions ram_used for example in this line:

  $n_output .= " | ram_used=" . ($$resultat{$nets_ram_total}-$$resultat{$nets_ram_free}-$$resultat{$nets_ram_cache}).";";

This strongly suggests that ram_used is calculated as the difference of the total RAM and the free RAM and the RAM used for cache. These values are retrieved via the following SNMP ids:

my $nets_ram_free   = "1.3.6.1.4.1.2021.4.6.0";  # Real memory free
my $nets_ram_total  = "1.3.6.1.4.1.2021.4.5.0";  # Real memory total
my $nets_ram_cache      = "1.3.6.1.4.1.2021.4.15.0"; # Real memory cached

I don't know how they correlate to the output of free. The difference in free memory reported by free and to Icinga is 48136, so maybe you can find that number somewhere.

How is memory used value derived in check_snmp_mem.pl?

1 Answers1