I have very interesting case to share

In order to improve database server performance on Oracle RAC one Node i introduce change on ASM - as memory allocation from 380M to 1.5GB.
Also HugePages is caviar of this topic

Additional details:
OS Linux - Red Hat Enterprise Linux Server release 6.2 (Santiago)
Oracle GI 11.2.0.3
Oracle DB 11.2.0.3
First database with Total 14GB SGA allocation
Second database with Total 3GB SGA allocation
---- script to calculate Huge Pages
Code:
#!/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' | '3.8') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;; *) echo "Unrecognized kernel version $KERN. Exiting." ;; esac # End --- check recomendation ./hugepages_settings.sh Recommended setting: vm.nr_hugepages = 8704
Will be good take into account future SGA change because in order to change to upper value you have to perform server/node restart.
So, i decided to add 80GB - this is -> vm.nr_hugepages = 40960
Simple add this in /etc/sysctl.conf
Code:
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