question.png

How to read in system commands and use them to calculate new variables ?

Bash script :

#!/bin/bash
#
# hugepages_settings.sh
#
# Linux bash script to compute values for the
# recommended HugePages/HugeTLB configuration
#
# Note: This script does calculation for all shared memory
# segments available when the script is run, no matter it
# is an Oracle RDBMS shared memory segment or not.
# Check for the kernel version
KERN=`uname -r | awk -F. '{ printf("%d.%d\n",$1,$2); }'`
# Find out the HugePage size
HPG_SZ=`grep Hugepagesize /proc/meminfo | awk {'print $2'}`
# Start from 1 pages to be on the safe side and guarantee 1 free HugePage
NUM_PG=1
# Cumulative number of pages required to handle the running shared memory segments
for SEG_BYTES in `ipcs -m | awk {'print $5'} | grep "[0-9][0-9]*"`
do
   MIN_PG=`echo "$SEG_BYTES/($HPG_SZ*1024)" | bc -q`
   if [ $MIN_PG -gt 0 ]; then
      NUM_PG=`echo "$NUM_PG+$MIN_PG+1" | bc -q`
   fi
done
# Finish with results
case $KERN in
   '2.4') HUGETLB_POOL=`echo "$NUM_PG*$HPG_SZ/1024" | bc -q`;
          echo "Recommended setting: vm.hugetlb_pool = $HUGETLB_POOL" ;;
   '2.6') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;
    *) echo "Unrecognized kernel version $KERN. Exiting." ;;
esac
# End

answer.png

"meminfo" string => execresult( "${paths.path[cat] /proc/meminfo", "noshell" );

memtotal::
"memtotal" string => "${mi_array[1]";

"myvar" string => execresult( "${paths.path[bc]} <<< '${SEG_BYTES / 2', "noshell" );

You might need useshell rather than noshell.

You can pull data from ${meminfo} using regextract.

classes:
"memtotal"
 expression => regextract(
   "(?i).*?memtotal:\s*(\d*).*",
   "${meminfo}",
   "mi_array"
   );

Answered by Neil Watson

sysctl.conf hugepages and variables calculation