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It has landed.

Submitted by gwolf on Wed, 08/12/2015 - 22:48

Basically everybody who knows me is aware that, basically for the last two years, I have been writing a book on Operating Systems for use in my class — and, of course, in any similar class. Well, long story short, as of today:

What's that in my car trunk? Lets have a closer look.

Finally, Facultad de Ingeniería finished printing the book!

So... Well, some minor data points:

  • The book is (and has been for some time already!) available online as a free download.
  • If you want to derive from it or enhance future editions in any way, just clone it!.
  • Want to get a physical copy? Great! It will soon (a week or so) be ready at both the Faculty's and the Institute's bookstores.
  • But coming to UNAM is hard for you? Stay tuned. I have uploaded it to an on-demand printing service (Bubok), but its service is so dismally slow that I'll try it somewhere else. I'll keep you posted!

Anyway... Very happy here :D

Finishing the course on "Free Software and Open Standards"

Submitted by gwolf on Fri, 07/10/2015 - 08:01

A couple of months ago, I was invited to give the starting course for the Masters degree in Free Software in the Universidad Andina Simón Bolívar university. UASB is a multinational university, with campuses in (at least) Ecuador, Chile, Bolivia and Colombia; I was doubtful at first regarding the seriousness of this proposal and the viability of the program, but time made my doubts disappear.

Bolivia is going through an interesting process, as they have one of the strongest worded government mandates for migration to free software for the public administration in the next couple of years; this migration has prompted the interest of many professionals in the country. In particular, we have over 40 registered people for this Masters degree. Studying a Masters degree is a long-term commitment which signifies a big time investment, and although many of the student are quite new to the idea of free software, they are willing to spend this time (and money, as the university is privately owned and charges for its enrollment).

I gave this class together with Alejandro Miranda (a.k.a. @pooka), as we have a very good pair-teaching dynamics; we had already given many conferences together, but this is the first time we had the opportunity to share a whole course — and the experience was very good. We have read the students' logs, and many of them clearly agree with this.

I had to skip two of the (ten) lessons, as I travelled from Mexico to Argentina halfway through it (of course, we brought the babies to meet my wife's family and friends!), so we had also the honor of having Esteban Lima fill in for those sessions.

I am very happy and grateful that the University took care to record our presentations and intend to record and put online all of the classes; as we were the first in the program, there were some understandable hiccups and some sessions were lost, but most are available. Here they are, in case you are interested in refering to them:

Topic Video (my server) Video (Youtube)
Introduction to free software Watch Watch
History Watch Watch
Free culture Watch Watch
The effects of free software Watch Watch
Free software and open standards related to technologic soverignity Watch (low)
Watch (high)
Watch (low)
Watch (high)
The free software ecosystem Watch Watch
Free software implementation in Bolivia Watch Watch
Introduction to intelectual property: Copyright, patents, trademarks, etc. Watch Watch
Who is "the community" and why do we speak about it? Watch (low)
Watch (high)
Watch (low)
Watch (high)
Current status and challenges for the movement Watch Watch

We have yet another video file (which I have not fully followed through) titled ADSIB - Migration plan. It can also be downloaded from my server or watched online at Youtube.

All in all: This was a great opportunity and a joy to do. I think the material we used and developed fit well what was expected from us, and we had fun giving somewhat heterodox readings on our movement.

[Update]: UASB uploaded some extra videos, with a much better quality! I added them to the table above, specifying (Low) or High whenever needed. Also, all classes are now available. Enjoy!

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Guests in the Classroom: Felipe Esquivel (@felipeer) on the applications on parallelism, focusing on 3D animation

Submitted by gwolf on Fri, 05/08/2015 - 10:44

I love having guests give my classes :)

This time, we had Felipe Esquivel, a good friend who had been once before invited by me to the Faculty, about two years ago. And it was due time to invite him again!

Yes, this is the same Felipe I recently blogged about — To give my blog some credibility, you can refer to Felipe's entry in IMDb and, of course, to the Indiegogo campaign page for Natura.

Felipe knows his way around the different aspects of animation. For this class (2015-04-15), he explained how traditional ray-tracing techniques work, and showed clear evidences on the promises and limits of parallelism — Relating back to my subject and to academic rigor, he clearly shows the speed with which we face Amdahl's Law, which limits the efficiency of parallelization at a certain degree perprogram construct, counterpointed against Gustafson's law, where our problem will be able to be solved in better detail given more processing abilities (and will thus not hit Amdahl's hard ceiling).

A nice and entertaining talk. But I know you are looking for the videos! Get them, either at my server or at

Guests in the classroom: César Yáñez (@caesarcomptus) talks about memory assignation algorithms

Submitted by gwolf on Wed, 04/08/2015 - 11:47

Once again, on March 11 I had a great guest to save me some work and give a talk at my class! This time it was César Yáñez, and he talked about memory management algorithms, emphasizing on ARC.

The video is available, both at this server and in

Thanks a lot!

Guests in the classroom: @Rolman talks about persistent storage and filesystems

Submitted by gwolf on Wed, 11/26/2014 - 10:49

On November 14, as a great way to say goodbye to a semester, a good friend came to my class again to present a topic to the group; a good way to sum up the contents of this talk is "everything you ever wondered about persistent storage".

As people who follow my blog know, I like inviting my friends to present selected topics in my Operating Systems class. Many subjects will stick better if presented by more than a single viewpoint, and different experiences will surely enrich the group's learning.

So, here is Rolando Cedillo — A full gigabyte of him, spawning two hours (including two hiccups where my camera hit a per-file limit...).

Rolando is currently a RedHat Engineer, and in his long career, he has worked from so many trenches, it would be a crime not to have him! Of course, one day we should do a low-level hardware session with him, as his passion (and deep knowledge) for 8-bit arcades is beyond any other person I have met.

So, here is the full video on my server. Alternatively, you can get it from The Internet Archive.

Guests in the classroom: @chemaserralde talks about real time scheduling

Submitted by gwolf on Wed, 10/29/2014 - 15:47

Last Wednesday I had the pleasure and honor to have a great guest again at my class: José María Serralde, talking about real time scheduling. I like inviting different people to present interesting topics to my students a couple of times each semester, and I was very happy to have Chema come again.

Chema is a professional musician (formally, a pianist, although he has far more skills than what a title would confer to him — Skills that go way beyond just music), and he had to learn the details on scheduling due to errors that appear when recording and performing.

The audio could use some cleaning, and my main camera (the only one that lasted for the whole duration) was by a long shot not professional grade, but the video works and is IMO quite interesting and well explained.

So, here is the full video (also available at The Internet archive), all two hours and 500MB of it for you to learn and enjoy!

Walking without crutches

Submitted by gwolf on Thu, 08/21/2014 - 00:34
Walking without crutches

I still consider myself a newbie teacher. I'm just starting my fourth semester. And yes, I really enjoy it.

Now, how did I come to teaching? Well, my training has been mostly on stages for different conferences. More technical, more social, whatever — I have been giving ~10 talks a year for ~15 years, and I must have learnt something from that.

Some good things, some bad habits.

When giving presentations, a most usual technique is to prepare a set of slides to follow/support the ideas. And yes, that's what I did for my classes: Since my first semester, I prepared a nice set of slides, thematically split in 17 files, with ~30 to ~110 pages each (yes, huge variation). Given the course spans 32 classes (72 hours, 2¼ hours per class), each slide lasts for about two classes.

But, yes, this tends to make the class much less dynamic, much more scripted, rigid, and... Boring. From my feedback, I understand the students don't think I am a bad teacher, but still, I want to improve!

So, today I was to give the introduction to memory management. Easy topic, with few diagrams and numbers, mostly talking about the intuitive parts of a set of functions. I started scribbling and shortening the main points on a piece of paper (yes, the one on the picture). I am sure I can get down to more reduction — But this does feel like an improvement!

The class was quite successful. I didn't present the 100% of the material (which is one of the reasons I cling to my presentations — I don't want to skip important material), and at some point I do feel I was a bit going in circles. However, Operating Systems is a very intuitive subject, and getting the students to sketch by themselves the answers that describe the working of real operating systems was a very pleasant experience!

Of course, when I use my slides I do try to make it as interactive and collaborative as possible. But it is often unfeasible when I'm following a script. Today I was able to go around with the group's questions, find my way back to the outline I prepared.

I don't think I'll completely abandon my slides, specially for some subjects which include many diagrams or pictures. But I'll try to have this alternative closer to my mind.

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Presenting Kaz!

Submitted by gwolf on Mon, 05/19/2014 - 16:27
Presenting Kaz!

My guest and good friend Kaz, ready to start explaining the ext4 filesystem (and kernel module)

Kaz explaining ext4

Submitted by gwolf on Mon, 05/19/2014 - 16:25
Kaz explaining ext4

Kaz explaining ext4

Submitted by gwolf on Mon, 05/19/2014 - 16:19
Kaz explaining ext4

Nice dinner at home after Kaz's presentation

Submitted by gwolf on Mon, 05/19/2014 - 16:18
Nice dinner at home after Kaz's presentation

With eclectic sushi and several other goodies.

Guest class: Jose Juan "Kaz" Casimiro ( @brit_kazito ) dissects the Ext4 filesystem module

Submitted by gwolf on Sat, 05/17/2014 - 16:49

Yesterday night, we had the opportunity to have –for the first time– my friend Kaz as a guest in my Operating Systems class. We are about to finish the semester, and he took the opportunity not just to show how the Ext4 filesystem is structured, but how it is implemented in a current Linux release.

Kaz took a very different approach from what I do: He did it really hands-on, starting with the explanation on how a hello world module would be created, and then digging in following the code of the ext4 module in Linux 3.14 (and some bits in the general filesystem-related includes).

Of course, for a ~2hr session, he did not go into the full details, but did show where the main structures of a filesystem are defined, including a general walkthrough on the general kernel coding style.

The class was very enjoyable and clear. We had the bad luck of the projector's lamp burning out at the beginning of the class, but still, you can see in the pictures the students were really into his exposition. I think the exposition did make it through and got the students involved and interested — And that makes it really worth it!

Now... Sadly, due to a (most probably) human factor, I tried to record this talk but lost most of it :-( I have only the first part, but lost most of the second one. I have some bits recorded by a second camera, but have to check if they make sense by themselves, or do need the whole context. Anyway, I'll be reviewing those bits, and will update this post when I get around to cleaning+fixing+integrating them.

Some more photos...

A talk by Kaz cannot be complete...

Submitted by gwolf on Sat, 05/17/2014 - 16:34
A talk by Kaz cannot be complete...

Until a cartoon version of one of the attendees is produced!

Nice dinner at home after Kaz's presentation

Submitted by gwolf on Sat, 05/17/2014 - 16:34
Nice dinner at home after Kaz's presentation

With eclectic sushi and several other goodies.

The students following Kaz's explanation of ext4

Submitted by gwolf on Sat, 05/17/2014 - 16:34
The students following Kaz's explanation of ext4

A full group of students following on Kaz's thorough explanation

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