sysctlgen - Generate useful /etc/sysctl.conf options

sysctlgen

#! /bin/sh

#
#  sysctlgen - Generate useful /etc/sysctl.conf options
#  Copyright (C) 2013 Matous J. Fialka, <http://mjf.cz/>
#  Released under the terms of The MIT License
#

#
#  Get PAGE_SIZE value from system compile-time variables
#
PAGE_SIZE=`
	getconf PAGE_SIZE
`

#
#  Get HUGE_PAGE_SIZE value from the running system
#
HUGE_PAGE_SIZE=`
	awk '/Hugepagesize/ { print $2 }' /proc/meminfo
`

#
#  Get MEM_TOTAL value from the running system
#
MEM_TOTAL=`
	awk '/MemTotal/ { print $2 }' /proc/meminfo
`

#
#  Round MEM_TOTAL value to the nearest power of 2 (important!)
#
MEM_TOTAL=`
	#  TODO: find some better (arithmetical) way to do this

	power=1

	while [ $power -lt $MEM_TOTAL ]
	do
		power=$(( power * 2 ))
	done

	echo $power

	unset power
`

#
#  Get KERNEL_SHM{MAX,MNI,ALL}_ORIG value from the running system
#
KERNEL_SHMMAX_ORIG=`
	sysctl -n kernel.shmmax
`
KERNEL_SHMMNI_ORIG=`
	sysctl -n kernel.shmmni
`
KERNEL_SHMALL_ORIG=`
	sysctl -n kernel.shmall
`

#
#  Set KERNEL_SHM{MAX,MNI,ALL} value according to the MEM_TOTAL and/or PAGE_SIZE
#
KERNEL_SHMMAX=$(( MEM_TOTAL * 1024 / 2 ))
KERNEL_SHMMNI=4096
KERNEL_SHMALL=$(( MEM_TOTAL * 1024 / PAGE_SIZE ))

#
#  Get VM_HUGEPAGES_ORIG value from the running system
#
VM_NR_HUGEPAGES_ORIG=`
	sysctl -n vm.nr_hugepages
`

#
#  Branch VM_NR_HUGEPAGES on the boundary of 4 GB of memory
#
if [ $MEM_TOTAL -gt 3145728 ]	#  > 3 GB (3 * 1024 * 1024)
then
	VM_NR_HUGEPAGES=$(( MEM_TOTAL / 2 / HUGE_PAGE_SIZE ))
else
	VM_NR_HUGEPAGES=0
fi

#
#  Generate /etc/sysctl.conf options
#
cat <<- EOT

#
#  <<>> KERNEL SHARED MEMORY <<>>
#

#
#  Original runtime value $KERNEL_SHMMAX_ORIG
#
kernel.shmmax		= $KERNEL_SHMMAX

#
#  Original runtime value $KERNEL_SHMMNI_ORIG
#
kernel.shmmni		= $KERNEL_SHMMNI

#
#  Original runtime value $KERNEL_SHMALL_ORIG
#
kernel.shmall		= $KERNEL_SHMALL

#
#  <<>> VIRTUAL MEMORY <<>>
#

#
#  Original runtime value $VM_NR_HUGEPAGES_ORIG
#
vm.nr_hugepages		= $VM_NR_HUGEPAGES

EOT

#
#  Unset all used variables
#
unset PAGE_SIZE
unset HUGE_PAGE_SIZE
unset MEM_TOTAL
unset KERNEL_SHMMAX_ORIG
unset KERNEL_SHMMNI_ORIG
unset KERNEL_SHMALL_ORIG
unset KERNEL_SHMMAX
unset KERNEL_SHMMNI
unset KERNEL_SHMALL
unset VM_NR_HUGEPAGES_ORIG
unset VM_NR_HUGEPAGES

#  vi:ft=sh