What does “perf interrupt took to long” mean?

Wifi problems…

So, I’m having a problem with my laptop. When I’m using the “TelenetWiFree” connection, I get disconnected after a certain amount of time, and for some reason I cannot reconnect until I restart my computer. Toggling the hardware Wifi kill-switch, which lets you disable and enable the power to the wifi hardware, does not resolve the problem. After re-enabling the hardware, the wifi doesn’t seem to come back again. Only a reboot makes the Wifi work again…

The “TelenetWiFree” Wifi doesn’t play well with all the computers we have, three Ubuntu laptops and one Chromebook, but it seems particularly wonky with my computer.  I had some free time, so I started digging into the problem.

Who watches the watchmen? It seems the kernel does…

In the dmesg output, I found the following line:

perf interrupt took too long (2528 > 2500), lowering kernel.perf_event_max_sample_rate to 50000

This doesn’t seem right, maybe this is the source of the problem! Let’s do some digging:

  • Perf is a Linux Kernel performance monitor.
  • Perf uses Non-Maskable Interrupts. This basically means Perf can tell the cpu “Pauze whatever you’re doing now and let me do something”. This allows perf to have a “watchdog” functionality where it can monitor even the most critical processes and interrupts.

With great power comes great responsibility. Perf can hang your computer by constantly pauzing everything. To make sure this won’t happen, the kernel itself monitors perf.  When it decides perf is pauzing too long, it tells perf to do a little bit less. That’s basically what that dmesg line means. The kernel told perf to do a little bit less. Does it have anything to do with the Wifi problem? Probably not… But at least I learned something: The kernel watches the watchmen…

Additional sources:

cat /meetup/pragmatic_docker_day_2015

I got a ticket to the Pragmatic Docker Day meetup in Ghent in exchange for writing a blogpost about it. Free food, drinks & awesome talks for a whole day, who would want to miss that? Not me!

So here are my unstructured thoughts I gathered from the meetup:

Docker is awesome!

What is docker? Docker encapsulates apps in their own little sandbox. Every app runs in its own container. An environment made especially so the app can run well and can’t mess to much with other apps running on the same server. It’s basically a VM without the overhead.

Docker is an open platform for developers and sysadmins to build, ship, and run distributed applications

Developers write their apps and put them in a docker container. They give this container to sysadmins and they are sure everything will work once deployed on the server because the app and all its dependencies are bundled in the docker container.

Docker is fancy!

This isn’t new at all. Containers have existed on Linux for a very long time. What docker does is provide a very fancy interface and API to work with and distribute those containers. This opens container technologies to a much broader public.

Docker is becoming so popular that even Microsoft wants in on the party. Docker announced a partnership with Microsoft to bring Docker to Windows.

Docker is production-ready*

Tomas Doran talked about how Yelp is using Docker in their Continues Integration & Continues Deployment workflow. From what I gathered, almost every service at Yelp is running in docker containers. This allows for very dynamic scaling, and makes the development – testing – production chain a lot shorter without compromising on the stability.

*Docker is still a very young and fast-moving platform. Using this in production requires a lot of knowledge and requires some caution. For a small infrastructure the benefits you get from docker might not outweigh the disadvantages from working with such early technology. However, even when you don’t use Docker in production, you can still benefit from it during development and testing!

Docker containers are not cross-platform…

The docker container still uses the host’s kernel. This means that a docker container will only work on a machine that supports the same kernel functionality. If you make a docker container on Linux, and you run it on a distro with a different version of the Linux kernel, most of the time you’ll be allright. However, running Linux docker containers native on a Mac or Windows won’t work.

You can still run containers on Windows?!

It’s still possible to run Linux docker containers on Mac and Windows using boot2docker. This is basically a lightweight Linux VM. Docker containers run in this VM. This is great for development, but there might be an overhead because of the virtualization.

Pragmatic Docker Day

Tuesday, Apr 21, 2015, 8:30 AM

Zebrastraat 32 9000 Gent, BE

1 Dockers Went

Important: RSVP/Subscriptions via eventbrite: http://bit.ly/pragmaticdockerdayThe main focus ‘pragmatic’ docker:Docker is awesome but doesn’t come with batteries included ; once you go beyond the simple docker you’ll be searching the web for insights and having to decide between the old/new/hottest approach to do things.I’ve noticed many docker …

Check out this Meetup →

Why you think Linux sucks (and why it’s your own fault)

Let’s rid the world of one of the most prominent Linux myths: “Desktop Linux sucks. It’s just not there yet”.

When Windows power users try out Linux two things always happen:

  1. They get frustrated because they can’t find how to do something in Linux.
  2. They brick their system, or make it extremely buggy.

I’ve been that person, I’ve bricked my system (a lot!), and the fact is, it was entirely my own fault. Linux didn’t suck, I made it suck! This post is a summary of every mistake I made the last 4 years, in an attempt to prevent other people from making the same ones.

dilbert-unixLet’s rid the world of a few Linux misconceptions

Linux is different

Let’s start with an example: Bill is trying out Ubuntu and wants to change his screen resolution. Bill knows that on Windows, you can right-click the desktop background and click “change screen resolution”. Bill tries this, but cannot find the “change screen resolution” option. Bill can now do two things:

  1. [the bad way] Assume you can only change this using the commandline. Go online and rant about how Ubuntu is impossibly hard to use.
  2. [the good way] Open the dash and search for “Resolution” or “screen” or “display” or “monitor” or “projector” or whatever. He will find the “Displays” application. If he isn’t entirely sure if that is the right application, he can right-click the icon and he will see a description of what the application does.

Linux is not Windows. You are used to doing things a certain way on Windows. Some things will work differently on Linux. You will have to get used to it. This does not mean Linux is hard, only that it is different. Mac has this exact same problem. Windows power users complaining that ctrl-c ctrl-v does not work on a mac, even though the command button makes a lot of sense.

Yes, you can change the resolution in a GUI

And yes, you can change the resolution in a GUI

Windows power user != Linux power user

Another example: Jessica knows a thing or two about Windows, she can even re-install Windows, if she finds that dvd she once burned. Jessica want to try out Ubuntu. She takes an old computer lying around and starts up the Ubuntu installer. She knows it’s better to have different partitions, so she chooses to partition the disks manually. She tries to configure the partitions, but she keeps getting errors she does not understand. She gets frustrated and rants on G+ about how in Linux, everything is complicated.

I see this mentality a lot: “I know how to do advanced tasks on Windows. I don’t know how to do advanced tasks on Linux, so Linux must be hard.”

You can do advanced tasks on Windows, because you learned how to do them on Windows. You will have to learn how to do some of them for Linux. This is the same for every platform. You can be a complete Linux Guru, being able to install Linux From Scratch. But you will still have to relearn how to flash your android phone.

Give it time, after a while you will come to have the same skill level on Linux as you have on Windows. Just don’t expect to get there on the first day.

You are a danger to your Linux

Exhibit A: Alice her Windows machine is becoming really slow and she wonders what she could do to speed it up a little. Alice googles “how to speed up Windows”. One of the first results is a blog explaining how to use cCleaner to disable processes. Alice, being a Windows power user, knows this can break her system really bad, so she is very careful and googles each process before disabling it. Alice is happy, her Windows is faster again.

Exhibit B: Bob is running the latest Ubuntu on a 10-year old laptop and notices it is a bit slow. Bob is a Windows power user, he figures he knows enough about computers to do something about it. He googles “how to make Ubuntu faster”. He finds a blog telling him to run different commands. The blogpost is a year old and has a lot of “thanks!” comments, so Bob thinks he can trust the author. Bob runs the commands. When a command fails, he figures it is a permission problem, so he runs the command again with “sudo”. The following week, Bob experiences weird glitches and crashes, and his computer cannot connect to his printer anymore. Bob is unhappy and goes on twitter to rage about how buggy Linux is.

You’re a Windows power user. You can mess with Windows, because you know what is dangerous, you know what warnings you can safely ignore. You are not a Linux power user. You do not know how to make that distinction on Linux, so be very careful!

make ubuntu faster

Do not blindly trust commands from the web

I cannot stress this enough. I’ve seen this happen so many times, with myself, and with other people.  A friend of mine wanted to make a lightweight Ubuntu install for a media center. He was using a heavily outdated guide to do so. The guide instructed him to remove a lot of programs, including compiz. Little did he know that newer versions of Ubuntu(Unity) require compiz to function properly. The result: he bricked his system, and blamed Ubuntu in the process.

A Desktop environment is not a theme

A desktop environment(DE) is a collection of software that does a lot more than just “look good”. A DE handles a lot of the “usability” features of the desktop, like automounting USB-sticks, CD’s, DVD’s and memory cards. It also helps you set up your network, it configures DHCP, detects wireless networks and gives you a nice user interface to enter the WIFI password. A DE also handles the function keys (brightness, sound, …) on your keyboard, and it can even connect to your smartphone to show you if you have new messages.

When you choose a DE, you basically choose how you will interact with your computer. If you choose a lightweight DE like lxde, you will lose a lot of the out-of-the-box experience a Windows/Mac user might expect. You will have to pop open a terminal, even to do basic stuff, like change your timezone. Unity on the other hand has those features, but demands more from your hardware.

Xubuntu might be fast and stable, but it comes with a price

Xubuntu might be fast and stable, but it comes with a price

A lot of the DE’s share the same libraries and software. Installing multiple DE’s at the same time can cause problems. If you want to try out different DE’s, I recommend doing a clean install with one of the official Ubuntu flavours, or another distro.

Choose wisely, and stick to that choice

Linux gives you a lot of choice. This is a great strength, but also a weakness. People have a tendency of making bad decisions when presented with so much choice.

Everyone who tried Linux for the first time has had the same question: “what distro should I use?”. This seems like a very hard question, and the internet gives you a lot of conflicting answers to it. However, for 99% of the people, the answer is really simple.

If you’re looking for a Window/Mac replacement for your primary machine, and you are new to Linux,  you should use default Ubuntu. Ubuntu offers the complete out-of-the-box experience you are used to on Windows/Mac. It is the best supported desktop, and It also has a good community that is very newbie-friendly. Every problem you will have, someone has had already. Askubuntu is full of questions Windows and Mac users might have when switching to Ubuntu.

Askubuntu, helping Windows users change to Linux since 2010

Askubuntu, helping Windows users change to Linux since 2010

You will surely find a DE that is easier to use than Unity. You will also find one that is more stable and one that is more beautiful. However, Unity offers the complete package with very few rough edges.

It’s also easy to find a Distro that is more up-to-date than Ubuntu. Finding one that is more stable and one that is faster is easy too. But again, Ubuntu offers the complete package, with very few rough edges. It makes the transition very easy and it is a care-free Windows/Mac replacement.

With a Numix theme, Unity looks pretty good!

With a Numix theme, Unity looks pretty good!


Are you thinking of joining the cool kids and trying out Linux? Then start with an easy distro like Ubuntu and be careful with what you do in the commandline. Most important of all, remember that Linux is different, and that’s a good thing.

Enjoy your Linux, and let me know your experiences in the comments down below.

CryTek and Star Citizen, two more victories in the battle for Gaming on Linux

One more company to put on the “Gaming on Linux” list: Crytek. A job posting reveals their intentions to bring the CryEngine to Linux. The CryEngine is famous for games like Far Cry, Crysis and the crowd-funding giant Star Citizen.


Star Citizen revealed their intentions to port the game to Linux a long time ago. They were very clear that, for that to happen, the CryEngine would have to be ported:

“The server side of CryEngine can run on Linux. Unfortunately the client side currently does not and is tied to DirectX.
We’ve been discussing OpenGL with them for Linux and Mac reasons and they have some other licenses that also want to do it, so it may happen in the near future.”

This is the future and it looks like it happened! So does this mean that Star Citizen will come to Linux? It does, According to Chris Roberts:

“I think that Linux and Mac owners will be happily surprised, when we can make an announcement we can’t just make yet.”

CryTek and Star Citizen, two more victories in the battle for Gaming on Linux

How to install Age of Empires II: HD Edition (steam) on Ubuntu

AOE2HD2As strange as it sounds, playing a Microsoft game on Linux is possible! And quite easy to do so…

These instructions should work for Ubuntu 12.04 and 14.04 with a legal copy of AOE2HD on Steam.

STEP 1: Install Steam with PlayOnLinux

The game is not available on Steam for Linux. We will have to install Steam for Windows using Wine. Playonlinux does al the downloading and configuration for you. You can find PlayOnLinux in the software center.

  1. In PlayOnLinux press the install button
  2. Search for steam and install it

Note: If you can’t find steam in PlayOnLinux, search for the game on their website and click on the “install” button. Now it should show up in the search results of PlayOnLinux.

STEP 2: Install Age of Empires II: HD Edition

  1. Start Steam (double-click “Steam” in PlayOnLinux)
  2. Click the install button

STEP 3: Rename launcher and remove vcredist folder

The launcher is a little bit buggy in Linux, so we have to make Steam skip that.

  1. Right click on Steam in PlayOnLinux
  2. Click “open application’s directory”
  3. Go to the folder SteamApps/common/Age2HD
  4. Rename “Launcher.exe” to “Launcher.exe.bak”
  5. Rename “AoK HD.exe” to “Launcher.exe”

Every time you start AOE, steam tries to install vcredist and fails. This isn’t a problem, but you have to wait a while before AOE can start. To prevent this from happening, do the following:

  1. Go to the folder SteamApps/common/Age2HD/_CommonRedist
  2. Remove the folder “vcredist”


You can now play AOE2HD on your Ubuntu, and enjoy listening to singing monks, building castles and killing turkeys. It is possible that you have to repeat step 5 after a game update. If you are still having problems, let me know in the comments section below.

PS: If AOE2HD breaks after an update, just re-install it, and it will work again.





On my system it works without doing these steps, but feel free to try them, if it does not work for you.

-nostartup launch option

  1. Right-click the installed Age of Empires and click “Properties”
  2. Click “Set Launch Options”
  3. Add “-nostartup” to the Launch options

Install Visual Studio Redistributable and directx manually

  1. Select Steam in PlayOnLinux
  2. Click “Configure”
  3. Click the “Install Components” tab
  4. Install vcrun2010
  5. Install d3dx9

Source: Age of Empires II: HD Edition [Linux+Wine] Works!

Vrijdag 3 mei: Die hp -_-

Bro. Venace geeft mij zijn computer. Er is iets mis mee. “Hij word heel warm en de batterij gaat niet lang mee. Een week geleden was het veel beter”. Hij vraagt mij hoelang ik er mee bezig ga zijn. Met een uitleg zoals die kan ik dat helemaal niet weten. Het probleem kan een simpele virus tot een serieus hardware probleem zijn. Gelukkig heeft hij backups genomen dus mag ik hem zolang houden als nodig.

Je moet weten dat dit net dezelfde computer is als een klasgenoot van mij heeft (had). Dat model van hp staat ervoor bekend om ZEER warm te worden zonder reden. Veel hoop op een deftige oplossing heb ik niet echt…

Ik begin met eens naar de power-settings te kijken. Die staan op een of ander automatisch-super-fancy-super-nutteloos hp-recommended powerplan. Maw: hp heeft een programma gemaakt om een functionaliteit die standaard in Windows zit over te nemen. Het programma van hp doet dat natuurlijk veel minder goed dan dat Windows dat doet + het is een extra programma dat constant draait dus dat verbruikt meer stroom. Ik zet het programma uit en zet het powerplan op de Windows standaard “energiebesparing”. Ik zet ook dat de processor maar op 60% moet draaien. Je hebt bijlange niet zoveel kracht nodig voor facebook en mails… Opeens verbruikt de computer veel minder en word hij niet meer warm. Goed begin dus!

De ventilator maakt echter een zeer raar geluid, dus ik doe hem eens open. Moeilijker gezegd dan gedaan. HP probeerde met het design van de laptop Apple na te doen waardoor de computer even moeilijk is om open te doen als een Apple. Na een hele tijd prutsen zit ik eindelijk aan de compleet ondergestofte ventilator. Ontstoffen + nieuwe koelpasta op de processor en het beestje zoemt weer zoals een pasgeboren babymugje.

Na nog wat nutteloze programma’s (bloathware) van de pc te halen geef ik hem terug aan Bro. Venace. Twee dagen later laat hij mij weten dat de computer beter dan ooit tevoren draait en dat ik zeer wel bedankt ben. A job well done!


PS: Wat laptopfabrikanten toch hebben met power-settings, ik weet het niet. Sinds Windows 7 zijn de standaardinstellingen super goed maar toch maken laptopfabrikanten hun eigen, slechter, programma om die instellingen te tweaken. De programma’s zien er meestal cooler uit maar je laptop gaat minder lang mee op batterij… Ik heb tot op heden nog geen programma tegengekomen dat het energiebeheer beter doet dan Windows zelf. Jij wel? Laat het mij zeker weten!

Je betaalt mensen om een programma te maken dat nutteloos is. Dat programma zorgt er voor dat de laptop slechter werkt, dus mensen denken dat de laptop slechter is. Je verliest hier toch dubbel aan? Meer uitgaven aan programmeurs en minder inkomsten van mensen die je laptop kopen. Waarom blijf je het dan doen?

Donderdag 2 mei: Toch hoop

Vandaag weer een hele dag in de brolcontainer gezeten gewapend met een scherm en een toetsenbord. Alle containers op de hoop-hoop aflopen en kijken waarvan de bios nog opstart.

Er is maar één stopcontact aanwezig, maar ik heb er 2 nodig. Een van de jongens van Maendeleo komt aandraven met een verdeelstekker. Een nieuw design van stekker blijkbaar maar kom, ik klaag niet.

Na een hele dag testen vind ik 6 computers waarvan de bios nog werkt. Een daarvan heeft zelfs een werkende windows 2000 installatie!

Ik bedank de jongen van maendeleo door een echte britse stekker op zijn verdeelstekker te solderen en vertrek content naar huis. ‘s avonds kijken we met zen allen “Brother Bear”. Iedereen heeft die film gezien als kind, behalve ik. Ik was te druk bezig met in een boom te kruipen ofzo..

Woensdag 1 mei: geen hoop

Nu er 5 man weg is, zijn er 3 kamers vrij. Tijd om eens van kamer te veranderen. Ik ben het beu om iedere morgen om 7 uur wakker te worden door de broeders die in de kamer ernaast zitten te ontbijten. ‘s avonds kan ik ook amper in slaap geraken want de kamer koelt langs geen kanten af. Doordat de kamer tussen 2 kamers ligt komt er niets van frisse wind binnen…

Mijn nieuwe kamer is nogal een upgrade! Een hemelbed met echte lattenbodem, een raam (gat met muggengaas) naar buiten, en heel de kamer voor mij alleen!

Na de verhuis en het vreugdedansje in mijn kamer vertrek ik naar het newman. Tijd om de hoop-hoop te doorzoeken achter computers die nog werken. We nemen 5 computers mee naar ons lokaal en beginnen er aan. Na een hele dag prutsen hebben we 5 computers die nog steeds niet werken. -_- Hopelijk hebben we morgen meer success…

Vandaag is er ook een trader langsgekomen om te kijken naar het computermateriaal dat we niet meer moeten hebben. Misschien kunnen we het nog verkopen zodat we een klein budget hebben om wat extra stukken te kopen. Hij is geïnteresseerd in de muizen en toetsenborden, maar hij wil nog eens een gesprek hebben over de prijs.

Dinsdag 30 april: Hopen

We zitten mooi op planning. Het is tijd om de brolcontainer uit te kuisen om te kijken of we enkele computers kunnne recupureren. Alle computers die we kunnen vermaken gaan naar Newman College om daar een deftige computerklas te maken.

We beginnen met alle complete brol weg te gooien. Gewapend met een stekker, een stopcontact en een scroevendraaier doen we de container open. Eén voor een halen we de computers er uit en kijken we of ze nog aan gaan. Eerst testen we de voeding, dan kijken we of de harde schijf draait en of de cdrom/dvd speler nog open gaat. Ook smijten we alle computers weg die echt te oud zijn (zoals een computer die nog een printer heeft ipv een scherm).

De computers die niet meer aan gaan halen we volledig uit elkaar. Alles wat wel nog werkt halen we er uit en daarna leggen we het lege skelet op de “geen-hoop-hoop”. Alles wat nog te redden valt leggen we op de “hoop-hoop”.



Terwijl ik de computers uit de container haal kom ik opeens op een computer vol gescheurd papier en kapotte plastiekzakken. Ik krijg wat argwaan en pak een stokje om er wat in te porren. Meneer de hele dikke muis komt vermoeid uit zijn nest en kijkt mij slaperig aan. Meneer de hele dikke muis werpt mij een blik van “wat komt gij hier doen” en hobbelt zo rustig als dat ge nog nooit een muis hebt zien hobbelen verder de container in. Met de computer van meneer de hele dikke muis kunnen we nietveel doen aangezien hij de computer heeft gebruikt als persoonlijke tandvijl.

Na een dag werken hebben kunnen we de helft van de computers op de “geen-hoop-hoop” leggen . Morgen kunnen we beginnen met de computers van de hoop-hoop te fixen.  We gaan naar het centrum om te vragen of er iemand geïnteresseerd is om oude/kapotte computers op te kopen. Na lang zoeken vinden we toch iemand die eens wil komen kijken. Een goed gebouwde Tanzaniaan met een bompa-klaksken geeft mij zijn nummer en wil morgen eens langskomen.

Things I did after installing Ubuntu Gnome 13.04

Chapter 1

Things I do after installation

First, I install the ambiance theme because the default gnome theme looks way to  Whity-KDEy-Appely-Fancy-Chromy. I get the feeling I’m standing in the middle of an ice desert, even though I’m in the middle of Africa sweating like a pig…

Then, I remove the menubar because why the hell is it still here? “A waste of space! A waste of space!”

Lastly, I install unity because this gnome-thing is as unstable as a 13-year old girl. Ever seen “The Virgin Suicides”? Yes? Then you know what I mean…

 Chapter 2

Why I still like it

Even though it is far too unstable, even for Ubuntu standards, I really like it. I will try it again in a few months, hoping it will be a little bit more stable. This is why I like it:

I REALLY like the activities panel. I think it is a way better design than the unity launcher. I like how much power the windows-key suddenly has. “want to switch to another window? Press windows!” “want to launch an app? Press windows!”. I also understand and the decision to remove the minimalize buttons because they are mostly used as a less-efficient way to switch between windows.

The hot-corner is the windows-key-master-goto-default-thingy for when you are working with your mouse. There are a lot of times when I’m working on my pc but my hands are not on my keyboard. Throwing my mouse in the left corner to be able to switch windows; it just seems natural to me.

Chapter 3


There are a few things that have really to change:

First, and most important: stability! stability! stability! I think the problem is with gnome 3.6 itself, because I had exactly the same experience with gnome on fedora. Then you should think about what to do with the “background-program-bar” because in this form, it’s an windows-8-like mess… Try to use dropbox and you’ll know what I mean. When all that is fixed, think about what to do with the menubar, because in this form, it is pretty much useless…

I have been using gnome 3.6. I have no idea if those things are fixed in gnome 3.8. If you know more about those things in gnome 3.8, feel free to let me know! If you have any idea how I can make it more stable, the comment section is at your disposal.