#!/bin/bash

#

# Copyright 2009 Red Hat, Inc. and/or its affiliates.

# Released under the GPL

#

# Author:      Dan Kenigsberg <danken@redhat.com>

#

# ksmtuned - a simple script that controls whether (and with what vigor) ksm

# should search for duplicated pages.

#

# starts ksm when memory commited to qemu processes exceeds a threshold, and

# make ksm work harder and harder untill memory load falls below that

# threshold.

#

# send SIGUSR1 to this process right after a new qemu process is started, or

# following its death, to retune ksm accordingly

#

# needs testing and ironing. contact danken@redhat.com if something breaks.

if [ -f /etc/ksmtuned.conf ]; then

    . /etc/ksmtuned.conf

fi

KSM_MONITOR_INTERVAL=${KSM_MONITOR_INTERVAL:-60}

KSM_NPAGES_BOOST=${KSM_NPAGES_BOOST:-300}

KSM_NPAGES_DECAY=${KSM_NPAGES_DECAY:--50}

KSM_NPAGES_MIN=${KSM_NPAGES_MIN:-64}

KSM_NPAGES_MAX=${KSM_NPAGES_MAX:-1250}

# millisecond sleep between ksm scans for 16Gb server. Smaller servers sleep

# more, bigger sleep less.

KSM_SLEEP_MSEC=${KSM_SLEEP_MSEC:-10}

KSM_THRES_COEF=${KSM_THRES_COEF:-20}

KSM_THRES_CONST=${KSM_THRES_CONST:-2048}

total=`awk '/^MemTotal:/ {print $2}' /proc/meminfo`

[ -n "$DEBUG" ] && echo total $total

npages=0

sleep=$[KSM_SLEEP_MSEC * 16 * 1024 * 1024 / total]

[ $sleep -le 10 ] && sleep=10

[ -n "$DEBUG" ] && echo sleep $sleep

thres=$[total * KSM_THRES_COEF / 100]

if [ $KSM_THRES_CONST -gt $thres ]; then

    thres=$KSM_THRES_CONST

fi

[ -n "$DEBUG" ] && echo thres $thres

KSMCTL () {

    case x$1 in

        xstop)

            echo 0 > /sys/kernel/mm/ksm/run

            ;;

        xstart)

            echo $2 > /sys/kernel/mm/ksm/pages_to_scan

            echo $3 > /sys/kernel/mm/ksm/sleep_millisecs

            echo 1 > /sys/kernel/mm/ksm/run

            ;;

    esac

}

committed_memory () {

    # calculate how much memory is committed to running qemu processes

    local progname

    progname=${1:-qemu}

    ps -o vsz `pgrep $progname` | awk '{ sum += $1 }; END { print sum }'

}

free_memory () {

    awk '/^(MemFree|Buffers|MemCached):/ {free += $2}; END {print free}' \

                /proc/meminfo

}

increase_npages() {

    local delta

    delta=${1:-0}

    npages=$[npages + delta]

    if [ $npages -lt $KSM_NPAGES_MIN ]; then

        npages=$KSM_NPAGES_MIN

    elif [ $npages -gt $KSM_NPAGES_MAX ]; then

        npages=$KSM_NPAGES_MAX

    fi

    echo $npages

}

adjust () {

    local free committed

    free=`free_memory`

    committed=`committed_memory`

    [ -n "$DEBUG" ] && echo committed $committed free $free

    if [ $[committed + thres] -lt $total -a $free -gt $thres ]; then

        KSMCTL stop

        [ -n "$DEBUG" ] && echo "$[committed + thres] < $total and free > $thres, stop ksm"

        return 1

    fi

    [ -n "$DEBUG" ] && echo "$[committed + thres] > $total, start ksm"

    if [ $free -lt $thres ]; then

        npages=`increase_npages $KSM_NPAGES_BOOST`

        [ -n "$DEBUG" ] && echo "$free < $thres, boost"

    else

        npages=`increase_npages $KSM_NPAGES_DECAY`

        [ -n "$DEBUG" ] && echo "$free > $thres, decay"

    fi

    KSMCTL start $npages $sleep

    [ -n "$DEBUG" ] && echo "KSMCTL start $npages $sleep"

    return 0

}

function nothing () {

    :

}

loop () {

    trap nothing SIGUSR1

    while true

    do

        sleep $KSM_MONITOR_INTERVAL &

        wait $!

        adjust

    done

}

PIDFILE=${PIDFILE-/var/run/ksmtune.pid}

if touch "$PIDFILE"; then

  loop &

  echo $! > "$PIDFILE"

fi