qemu-kvm/ksmtuned

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#!/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
debug() {
if [ -n "$DEBUG" ]; then
s="`/bin/date`: $*"
[ -n "$LOGFILE" ] && echo "$s" >> "$LOGFILE" || echo "$s"
fi
}
KSM_MONITOR_INTERVAL=${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`
debug total $total
npages=0
sleep=$[KSM_SLEEP_MSEC * 16 * 1024 * 1024 / total]
[ $sleep -le 10 ] && sleep=10
debug sleep $sleep
thres=$[total * KSM_THRES_COEF / 100]
if [ $KSM_THRES_CONST -gt $thres ]; then
thres=$KSM_THRES_CONST
fi
debug 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 $3 > /sys/kernel/mm/ksm/sleep_millisecs
echo 1 > /sys/kernel/mm/ksm/run
;;
esac
}
committed_memory () {
# calculate how much memory is committed to running qemu processes
local pidlist
pidlist=$(pgrep -d ' ' -- '^qemu(-(kvm|system-.+)|:.{1,11})$')
if [ -n "$pidlist" ]; then
ps -p "$pidlist" -o rsz=
fi | awk '{ sum += $1 }; END { print 0+sum }'
}
free_memory () {
awk '/^(MemFree|Buffers|Cached):/ {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`
debug committed $committed free $free
if [ $[committed + thres] -lt $total -a $free -gt $thres ]; then
KSMCTL stop
debug "$[committed + thres] < $total and free > $thres, stop ksm"
return 1
fi
debug "$[committed + thres] > $total, start ksm"
if [ $free -lt $thres ]; then
npages=`increase_npages $KSM_NPAGES_BOOST`
debug "$free < $thres, boost"
else
npages=`increase_npages $KSM_NPAGES_DECAY`
debug "$free > $thres, decay"
fi
KSMCTL start $npages $sleep
debug "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