Weekly Snap: CPU Limit, MOTP, Typed Arrays & Training Courses in 2012

19 – 23 September tried new tools such as CPUlimit.sh, mobile one-time passwords, and typed arrays in java script, while preparing for a municipal IT conference and training courses in 2012.
Birger began the week with his discovery of cpulimit.sh, a tool to cool down his over active MacBook Pro. With a 2.2 GHz Intel Core i7, it would often go into “jet mode” when indexing for Spotlight or running the video player, making a lot of noise in the process. On one hand he can easily switch off his graphics card with gfxCardStatus, however to reduce his CPU and energy consumption (thereby saving his battery and hearing) he found cpulimit.sh and a variant for those running on Lion.
Following on, Marcus H showed how to implement single-use password authentication with MOTP, the Mobile One Time Password project. He gave an example with an Apache module and an iOS client. First he compiled mod_authn_otp and installed dependencies per the MOTP project wiki. The module is treated like a normal basic auth in the Apache config. Here, a user file is given, where the corresponding user and their ‘secrets’ and the related PINs are specified. This file must be writeable by the Apache user, so that the module can set a timestamp. In this way, the token given to the user is valid only for a fixed time period and they will not be repeatedly asked for a new token. For the client, Marcus downloaded mOTP from the App Store. He recommended the guides on the project’s wiki for other operating systems such as Python.
From the development team, Jannis then had a look at low-level memory access in java script with typed arrays. The new data types, array buffer and typed arrays are used to access binary data effectively. Comparing the performance of internal arrays to the float 32 array, he concluded that float 32 array is worth trying for large amounts of data.
Bernd looked forward to the upcoming Kommunale and its premiere IT sub-conference 2011 in Nuremberg on 19 – 20 October. With a special focus on digital information and communication technologies in the municipality, the program covers cloud computing, DMS systems, Green IT and more. NETWAYS will join, with Bernd presenting on “IT Monitoring & Management Systems in Public Administration”. For help with tickets, contact our team at info@netways.de
Looking ahead, Markus N announced the NETWAYS course timetable for the start of 2012: Nagios Availability Monitoring on 16 – 19 January and Icinga Availability Monitoring on 16 – 20 January. Class sizes are restricted to 10 attendees for intensive learning, whilst allowing for discussion to consolidate course material. All-inclusive packages offer just that: accommodation (also on the course eve), catering, notebook hire, wlan internet, as well as a dinner and drinks event. If you are looking for tailored training however, the NETWAYS training team also offers workshops with customised material, run on-site at your office. More information is available at the NETWAYS training center.

Wenn das MacBook zu heiß ist – cpulimit.sh

Ich mag laute Hardware nicht. Und ich fand es gut, dass mein iBook mit 600MHz PowerPC G3 Prozessor aus dem Jahr 2001 nur im absoluten Notfall den Lüfter eingeschaltet hat. Auch mein MacBook Pro mit 2,4GHz Intel Core 2 Duo Prozessor war im Normalfall nicht zu hören.
Aber mein neues MacBook Pro mit 2,2GHz Intel Core i7 erdreistet sich, bei verschiedenen Gelegenheiten, in den “Jet-mode” zu gehen. Die Ursache ist dann gern mal der Indexer für Spotlight (metadata server – mds) oder ein Video Player (video lan client – vlc). Beide brauchen eigentlich nicht mit voller Power zu laufen um meinen Ansprüchen gerecht zu werden. Ausserdem braucht man meist auch die dedizierte Grafikkarte nicht. Die kann man aber Dank gfxCardStatus einfach abschalten. Achtung, nicht vergessen wieder anzuschalten, wenn man den Beamer dranhängt!
Apple hat leider keine Möglichkeit vorgesehen die CPU zu drosseln um weniger Strom zu verbrauchen und somit den Akku und das Gehör zu schonen. Todtraurig!
Nice ist auch keine Lösung, weil ja dennoch die Power genutzt wird die zur Verfügung steht.
Aber ich habe etwas gefunden was an dieser Stelle weiterhelfen kann: cpulimit. Das ließ sich aber unter Lion nicht compilieren. Es gibt da aber noch diese Variation davon.
An der Shell Variante habe ich ein wenig gefeilt. Nun bekommt man eine Liste der CPU hungrigen Prozesse zur Auswahl und den Erstplatzierten als Vorauswahl.
Das Ergebnis sieht dann so aus:

$ sudo ~/bin/cpulimit.sh
  This script will throttle a chosen process as you like it.
  Therefore your cpu runs cooler - hopefully.
Chose which process to throttle:
    1    66 root            25,5  5,1 Do08am   73:25.42  32:24.31 mds
  273   436 bschmidt        23,1  0,1 Do08am    1:20.18   0:13.72 Folder Actions Dispatcher
    1 19304 root            15,3  0,1 Sa03pm   62:40.11  51:14.03 activitymonitord
  273 91519 bschmidt        14,6  0,3  7:57pm   0:06.47   0:02.17 mdworker
    1    12 _mdnsresponder  12,6  0,0 Do08am   26:20.00  19:02.96 mDNSResponder
  273 91189 bschmidt        11,6  0,4  7:55pm   0:06.54   0:02.21 mdworker
  273 91520 bschmidt        11,3  0,3  7:57pm   0:06.48   0:02.17 mdworker
  273 91518 bschmidt         9,2  0,3  7:57pm   0:06.36   0:02.14 mdworker
  273 13471 bschmidt         8,7  3,6 Fr02pm  101:01.25  22:25.71 Google Chrome
Which process ID (PID) [guess: 66]?
   66 root  21,9  5,1 Do08am   73:26.43 /System/Library/Frameworks/CoreServices.framework/Frameworks/Metadata.framework/Support/mds
Sleep time in seconds (e.g 0.5 or 1 …) [default: 0.5]?
Run time in seconds (e.g 0.5 or 1 …) or percent [default: .5000 = 50%]?
OK. I will throttle PID 66 now and dislay processinfo every 20 seconds …
   66 root  40,5  4,7 Do08am   73:34.02 /System/Library/Frameworks/CoreServices.framework/Frameworks/Metadata.framework/Support/mds
   66 root  32,7  4,8 Do08am   73:34.91 /System/Library/Frameworks/CoreServices.framework/Frameworks/Metadata.framework/Support/mds
   66 root   0,0  4,8 Do08am   73:35.15 /System/Library/Frameworks/CoreServices.framework/Frameworks/Metadata.framework/Support/mds
*** Ouch! Stop throtteling of PID 66. Exiting ***

Mit diesem Script ist es ein Leichtes, Prozesse ausser Rand und Band wieder einzufangen. Erstaunlicher Weise sogar den Video Player, wenn man nur die sleep time kurz genug wählt.
Da das Script nicht lang ist, stell ich es hier einfach mal rein:

#! /bin/bash
# Description:
# If you want to decrease the CPU demands for an application
# you can use this very simple and ugly "hack".
# I use it when I convert videos on my MacBook Pro
# to prevent it from getting to warm. Even if the CPU is IDLE this hack
# will prevent the application to use the CPU during Sleep Time
# (in contrast to renice/nice commands which will take all IDLE time).
# This means the conversions will take longer time, but I
# don't care because I run it at night.
# There is similar c program for Linux called cpulimit, but it wont
# compile on my Mac.
# Usage:  sudo ./cpulimit.sh
# config
sleeptime_default=0.5   # in seconds
runtimep_default=50     # in percent (50 = same as sleeptime)
reporttime=30           # report every x seconds while running
# PROCESSLISTformat: pid has to be on the second position
# dont change anything below here
scriptuser=$(id -u)
# run if user hits control-c
  echo ""
  if [ "$pid" != "" ]; then
    echo -en "\n*** Ouch! Stop throtteling of PID $pid. Exiting ***\n"
    kill -SIGCONT $pid
  echo ""
  exit $?
# trap keyboard interrupt (control-c)
trap control_c SIGINT
  # takes pid as argument
  ps -p $1 -w -o pid,user,%cpu,%mem,start,cputime,command 2>/dev/null
  if [[ "$1" =~ ^[0-9]*([.][0-9]+)?$ ]] ; then
    return 0
    return 1
# main
cat << EOF
  This script will throttle a chosen process as you like it.
  Therefore your cpu runs cooler - hopefully.
if [ "$scriptuser" != "0" ]; then
cat << EOF
  You're not root!
  If you want to controll processes that you dont own,
  please run via sudo.
until [ "$PIDSTRING" != "" ]; do
  #PROCESSLIST=$(ps -r -A -f -S | head)
  if [ "$scriptuser" != "0" ]; then
    PROCESSLIST=$(ps -r -u $scriptuser -S -c -o $PROCESSLISTformat 2>/dev/null)
    PROCESSLIST=$(ps -r -A -S -c -o $PROCESSLISTformat 2>/dev/null)
  if [ "$PROCESSLIST" = "" ]; then
    echo -en "\n*** Sorry, ps dont work as expected on $(uname). Exiting ***\n\n"
    exit 1
    PROCESSLIST=$(echo "$PROCESSLIST" | head)
  echo -en "\nChose which process to throttle:\n$PROCESSLIST\n"
  PID_GUESS=$(echo "$PROCESSLIST" | head -2 | tail -1 | awk '{print $2}')
  echo -n "Which process ID (PID) [guess: $PID_GUESS]? "
  read pid
  if [ "$pid" = "" ]; then
  # test if $pid is valid
  PIDSTRING=$(pidstring $pid)
  if [ "$?" -eq "0"  ]; then
    echo -en "\nChosen:\n$PIDSTRING\n"
    echo -en "\n$pid is not a valid PID for a running process.\n"
  echo -en "\n"
until [ "$sleeptime" != "" ]; do
  echo -n "Sleep time in seconds (e.g 0.5 or 1 …) [default: $sleeptime_default]? "
  read sleeptime
  if [ "$sleeptime" = "" ]; then
  isnumber $sleeptime || sleeptime=""
#echo "sleeptime $sleeptime"
until [ "$runtime" != "" ]; do
  runtime_default=$(echo "scale=4;$sleeptime*$runtimep_default/(100-$runtimep_default)"|bc)
  echo -n "Run time in seconds (e.g 0.5 or 1 …) or percent [default: $runtime_default = $runtimep_default%]? "
  read runtime
  if [[ "$runtime" =~ ^([0-9]*([.][0-9]+)?)%$ ]] ; then
  if [ "$runtime" = "" ]; then
  isnumber $runtime || runtime=""
#echo "runtime $runtime"
# now begin throttle
looptime=$(awk "BEGIN { printf \"%.0f\\n\", ($sleeptime+$runtime)*100 }")
echo "OK. I will throttle PID $pid now and dislay processinfo every $reporttime seconds … "
while true
  if [ $throttletime -ge 500 ]; then
    PIDSTRING=$(pidstring $pid)
    echo "$PIDSTRING"
  kill -SIGSTOP $pid || control_c
  sleep $sleeptime
  kill -SIGCONT $pid || control_c
  sleep $runtime