header image
Trashing Chromebooks
June 5th, 2014 under Computers, Hardware, rengolin, Unix/Linux. [ Comments: 9 ]

At Linaro, we do lots of toolchain tests: GCC, LLVM, binutils, libraries and so on. Normally, you’d find a fast machine where you could build toolchains and run all the tests, integrated with some dispatch mechanism (like Jenkins). Normally, you’d have a vast choice of hardware to chose from, for each different form-factor (workstation, server, rack mount) and you’d pick the fastest CPUs and a fast SSD disk with space enough for the huge temporary files that toolchain testing produces.


The only problem is, there aren’t any ARM rack-servers or workstations. In the ARM world, you either have many cheap development boards, or one very expensive (100x more) professional development board. Servers, workstations and desktops are still non-existent. Some have tried (Calxeda, for ex.) but they have failed. Others are trying with ARMv8 (the new 32/64-bit architecture), but all of them are under heavy development, so not even Alpha quality.

Meanwhile, we need to test the toolchain, and we have been doing it for years, so waiting for a stable ARM server was not an option and still isn’t. A year ago I took the task of finding the most stable development board that is fast enough for toolchain testing and fill a rack with it. Easier said than done.


Amongst the choices I had, Panda, Beagle, Arndale and Odroid boards were the obvious candidates. After initial testing, it was clear that Beagles, with only 500MB or RAM, were not able to compile anything natively without some major refactoring of the build systems involved. So, while they’re fine for running remote tests (SSH execution), they have very little use for anything else related to toolchain testing.


Pandas, on the other hand, have 1GB or RAM and can compile any toolchain product, but the timing is a bit on the wrong side. Taking 5+ hours to compile a full LLVM+Clang build, a full bootstrap with testing would take a whole day. For background testing on the architecture, it’s fine, but for regression tracking and investigative work, they’re useless.

With the Arndales, we haven’t had such luck. They’re either unstable or deprecated months after release, which makes it really hard to acquire them in any meaningful volumes for contingency and scalability plans. We were left then, with the Odroids.


HardKernel makes very decent boards, with fast quad-A9 and octa-A15 chips, 2GB of RAM and a big heat sink. Compilation times were in the right ball park (40~80 min) so they’re good for both regression catching and bootstrapping toolchains. But they had the same problem as every other board we tried: instability under heavy load.

Development boards are built for hobby projects and prototyping. They normally can get at very high frequencies (1~2 GHz) and are normally designed for low-power, stand-by usage most of the time. But toolchain testing involves building the whole compiler and running the full test-suite on every commit, and that puts it on 100% CPU usage, 24/7. Since the build times are around an hour or more, by the time that the build finishes, other commits have gone through and need to be tested, making it a non-stop job.

CPUs are designed to scale down the frequency when they get too hot, so throughout the normal testing, they stay stable at their operating temperatures (~60C), and adding a heat sink only makes it go further on frequency and keeping the same temperature, so it won’t solve the temperature problem.

The issue is that, after running for a while (a few hours, days, weeks), the compilation jobs start to fail randomly (the infamous “internal compiler error”) in different places of different files every time. This is clearly not a software problem, but if it were the CPU’s fault, it’d have happened a lot earlier, since it reaches the operating temperature seconds after the test starts, and only fails hours or days after they’re running full time. Also, that same argument rules out any trouble in the power supply, since it should have failed in the beginning, not days later.

The problem that the heat sink doesn’t solve, however, is the board’s overall temperature, which gets quite hot (40C~50C), and has negative effects on other components, like the SD reader and the card itself, or the USB port and the stick itself. Those boards can’t boot from USB, so we must use SD cards for the system, and even using a USB external hard drive with a powered USB hub, we still see the failures, which hints that the SD card is failing under high load and high temperatures.

According to SanDisk, their SD cards should be ok on that temperature range, but other parties might be at play, like the kernel drivers (which aren’t build for that kind of load). What pointed me to the SD card is the first place was that when running solely on the SD card (for system and build directories), the failures appear sooner and more often than when running the builds on a USB stick or drive.

Finally, with the best failure rate at 1/week, none of those boards are able to be build slaves.


That’s when I found the Samsung Chromebook. I had one for personal testing and it was really stable, so amidst all that trouble with the development boards, I decided to give it a go as a buildbot slave, and after weeks running smoothly, I had found what I was looking for.

The main difference between development boards and the Chromebook is that the latter is a product. It was tested not just for its CPU, or memory, but as a whole. Its design evolved with the results of the tests, and it became more stable as it progressed. Also, Linux drivers and the kernel were made to match, fine tuned and crash tested, so that it could be used by the worst kind of users. As a result, after one and a half years running Chromebooks as buildbots, I haven’t been able to make them fail yet.

But that doesn’t mean I have stopped looking for an alternative. Chromebooks are laptops, and as such, they’re build with a completely different mindset to a rack machine, and the number of modifications to make it fit the environment wasn’t short. Rack machines need to boot when powered up, give 100% of its power to the job and distribute heat efficiently under 100% load for very long periods of time. Precisely the opposite of a laptop design.

Even though they don’t fail the jobs, they did give me a lot of trouble, like having to boot manually, overheating the batteries and not having an easy way to set up a Linux image easily deployable via network boot. The steps to fix those issues are listed below.

WARNING: Anything below will void your warranty. You have been warned.

System settings

To get your Chromebook to boot anything other than ChromeOS, you need to enter developer mode. With that, you’ll be able not only to boot from SD or USB, but also change your partition and have sudo access on ChromeOS.

With that, you go to the console (CTRL+ALT+->), login with user chronos (no password) and set the boot process as described on the link above. You’ll also need to set sudo crossystem dev_boot_signed_only=0 to be able to boot anything you want.

The last step is to make your Linux image boot by default, so when you power up your machine it boots Linux, not ChromeOS. Otherwise, you’ll have to press CTRL+U every boot, and remote booting via PDUs will be pointless. You do that via cgpt.

You need to find the partition that boots on your ChromeOS by listing all of them and seeing which one booted successfully:

$ sudo cgpt show /dev/mmcblk0

The right partition will have the information below appended to the output:

Attr: priority=0 tries=5 successful=1

If it had tries, and was successful, this is probably your main partition. Move it back down the priority order (6-th place) by running:

$ sudo cgpt add -i [part] -P 6 -S 1 /dev/mmcblk0

And you can also set the SD card’s part to priority 0 by doing the same thing over mmcblk1

With this, installing a Linux on an SD card might get you booting Linux by default on next boot.

Linux installation

You can chose a few distributions to run on the Chromebooks, but I have tested both Ubuntu and Arch Linux, which work just fine.

Follow those steps and insert the SD card in the slot and boot. You should get the Developer Mode screen and waiting for long enough, it should beep and boot directly on Linux. If it doesn’t, means your cgpt meddling was unsuccessful (been there, done that) and will need a bit more fiddling. You can press CTRL+U for now to boot from the SD card.

After that, you should have complete control of the Chromebook, and I recommend adding your daemons and settings during the boot process (inid.d, systemd, etc). Turn on the network, start the SSD daemon and other services you require (like buildbots). It’s also a good idea to change the governor to performance, but only if you’re going to use it for full time heavy load, and especially if you’re going to run benchmarks. But for the latter, you can do that on demand, and don’t need to leave it on during boot time.

To change the governor:

$ echo [scale] | sudo tee /sys/bus/cpu/devices/cpu[N]/cpufreq/scaling_governor

scale above can be one of performance, conservative, ondemand (default), or any other governor that your kernel supports. If you’re doing before benchmarks, switch to performance and then back to ondemand. Use cpuN as the CPU number (starts on 0) and do it for all CPUs, not just one.

Other interesting scripts are to get the temperatures and frequencies of the CPUs:

$ cat thermal
#!/usr/bin/env bash


for dir in $ROOT/*/temp; do
temp=`cat $dir`
temp=`echo $temp/1000 | bc -l | sed 's/0\+$/0/'`
device=`dirname $dir`
device=`basename $device`
echo "$device: $temp C"

$ cat freq
#!/usr/bin/env bash


for dir in $ROOT/*; do
if [ -e $dir/cpufreq/cpuinfo_cur_freq ]; then
freq=`sudo cat $dir/cpufreq/cpuinfo_cur_freq`
freq=`echo $freq/1000000 | bc -l | sed 's/0\+$/0/'`
echo "`basename $dir`: $freq GHz"

Hardware changes


As expected, the hardware was also not ready to behave like a rack server, so some modifications are needed.

The most important thing you have to do is to remove the battery. First, because you won’t be able to boot it remotely with a PDU if you don’t, but more importantly, because the head from constant usage will destroy the battery. Not just as in make it stop working, which we don’t care, but it’ll slowly release gases and bloat the battery, which can be a fire hazard.

To remove the battery, follow the iFixit instructions here.

Another important change is to remove the lid magnet that tells the Chromebook to not boot on power. The iFixit post above doesn’t mention it, bit it’s as simple as prying the monitor bezel open with a sharp knife (no screws), locating the small magnet on the left side and removing it.


With all these changes, the Chromebook should be stable for years. It’ll be possible to power cycle it remotely (if you have such a unit), boot directly into Linux and start all your services with no human intervention.

The only think you won’t have is serial access to re-flash it remotely if all else fails, as you can with most (all?) rack servers.

Contrary to common sense, the Chromebooks are a lot better as build slaves are any development board I ever tested, and in my view, that’s mainly due to the amount of testing that it has gone through, given that it’s a consumer product. Now I need to test the new Samsung Chromebook 2, since it’s got the new Exynos Octa.


While I’d love to have more options, different CPUs and architectures to test, it seems that the Chromebooks will be the go to machine for the time being. And with all the glory going to ARMv8 servers, we may never see an ARMv7 board to run stably on a rack.

Asperger’s and the failure of the educational system
December 28th, 2013 under Life, rengolin, World. [ Comments: none ]

Asperger’s Syndrome (more info), a condition within the Autism spectrum where social awareness is lacking, but communication skills are not affected much, is a topic floating around our house for a few years. After many ups and downs, our son has finally been diagnosed with it, and the rest of the family will need serious checking, too.

That has brought us many explanations to most of our problems at work and school, and got me thinking on many of the issues I found illogical in the educational system, but always though it was my fault for not adapting to it. Now, the more I think, the more I realise that any system that base teaching on the average child is, to say the least, mediocre.

On a large scale, children (and adults), range from very low to very high skills in many areas, from IQ, to social, to artistic or empathic skills. With so many different dimensions, and so many scales focused on defining people for what they are, and so many different types of peoples around, trying to create the imaginary “average child” to educate is a folly quest. But a lot more serious than folly, is the quest to force different children to accommodate to that imaginary average and brutalise them when they don’t. There is a name for it: bullying.

Schools are well known for not caring much for the “lesser minds“, since they don’t contribute much to the scoring system, under disability Acts, they’re free to refer those problematic children to special schools, where they will be marginalised and receive funding from the government for the rest of their lives, even though, if thought well, they could perfectly have a decent living by themselves.

But the brightest children are also in peril, for they do contribute to scoring, and in a positive way. They’re sought after by schools that have no idea on how to educate those children. With the failure to understand their advanced needs, those kids become repugnant braggarts. Even though they can go beyond on arts, maths or science, most of them lack any social skills or, for the very definition of “special“, fail miserably to conform to the “average child” norm.

The expectation that special children have the same traits as average children, plus a few special skills, is idiotic, and I’m really surprised that this has passed in so many countries and educational systems as the norm to be followed, and imposed. It shows that whomever is dealing with educating the brightest minds are not brightest minds themselves. It’s the same as giving the job to rehabilitate petty criminals to serial killers.

Scoring System

The very notion of scoring system is at the core of the standardisation of the human race.

Each group in society has a different take on what’s important for their cohesion. Some rely on competition and selfish behaviour to keep the capitalism alive and kicking, others rely on knowledge and logical thinking to progress science, and so on. This diversity is paramount to define the human race as a multi-cultural species, where every aspect of it is as valuable as every other.

The notion of a National Curriculum is a good one, since even the most artistic ones have to be able to add up at the grocery store, and the brightest mathematicians should be able to plat instruments, if they so chose. But what happens in most schools, and certainly in all public schools we’ve been in England, so far, it’s that they treat the curriculum as a golden standard, and don’t even attempt to go beyond.

The same way when you’re speeding on the road, and the policeman stop you and say “The speed limit is a limit, not a guideline”, the National Curriculum is a minimum, not a guideline. It means that, if you’re not teaching at least that, you should not be called a “school” to begin with. But it also means that you should go beyond, at least for the children that have the capacity to follow.

No child will follow on every category, so you need to know what each child can do on each extra topic. That also means that, while the least able children will have at least the National Curriculum, the average children will have more in different areas, and the only difference between the average and the above-average children is the amount of extra subjects and topics they learn. It’s that simple.


But for it to be that simple, the way exams work have to change completely. Exams today don’t test for what a child knows or have learnt, but it tests for what they are able to memorise in a short term, or how effectively they can guess, or how efficiently they can cheat.

Take, for example, the SAT tests, which are the exams taken by all children between primary and secondary schools. The format here is to fill the blanks. It’s a lot better than multiple choice, even though there are many questions in it that are multiple choice there, but it’s not testing the ability of children to think at all.

It is true that average children will have to think to answer those questions. It is also true that average children will have to have learnt that in the first place by listening and memorising the concepts, but not necessarily understood why they’re like that. There seems to be no questions about why the universe behaves in that way, or why I can solve the same mathematical problem in different ways and still get the same results.

But the biggest failure is that the tests are standardised to the National Curriculum, and standardised to what an ideal average child will be able to understand and answer from her memory. In the age of the technological revolution, we have to ask ourselves if this is the right way forward.

Do we want to continue forcing people to follow averages, if we want humans to be a better species? Do we need more average people doing specialised work? Isn’t our technological level ready for a de-centralised, de-normalised learning experience, which will fare a lot better on all non-average children in the world (ie. all children), and allow better matching to their own skills, desires and abilities?

One such way would be to have more meaningful questions, with non-obvious answer, and software to analyse them. So, instead of drawing the circulatory system and asking children to fill the lines pointing to organs with names, ask them to describe how the blood circulates inside the body. True, natural language processing is still not there yet, but there are a number of different ways to ask questions and make sure that the answer will be simple enough to be dealt with simple regular expressions or state machines that, in context, will be limited to only a number of valid answers.

Each answer will lead to different following questions, based on the answer, and each new step will take you towards harder or easier questions, or more specific to one topic or another. Recording the paths for each child will also tell you what are the missing knowledge in each child, and what topics the teachers have to cover more in depth, in general.

Personalised learning per se is not optimal, as I have seen myself with the Khan academy and programming books. My son could easily write new programs, and they would certainly work, but he couldn’t explain to me why. It was only when I intervene that he starting to understand why, but the attitude remains: he won’t need to understand why while questions, exams and results are measured by multiple choice, filling the blanks or guessing the answer.

Asperger’s disadvantage

Among intelligent people, those with Asperger’s have a serious disadvantage: as with other types of Autism, they can pattern match instinctively, and come up with accurate results without knowing how they did it. During primary school this is a huge advantage, since all questions are too silly to matter, but as you progress to secondary school (or worse, if you have a perfectionist father), you’ll have more and more difficulties in answering the questions that really matter: why?

Knowing “why” is fundamental because of reproducibility. Science is all about method. Mathematics is only consistent because it has a single method. Science follow suite, and is only consistent because it’s based on maths. This consistency comes in the form of reproducibility. If you can describe your method, and others can follow, than you have a proof, or a theory. Otherwise, it’s pseudo-science, or religion.

If one wants to answer questions, not just get them right on average, one wants to understand why certain method works, on which cases, with which constraints. If you spent your whole (short) life guessing and getting accurate answers (not necessarily correct ones), and if all the school cares is to be reasonably correct, than you’ll think you’re a genius (the school will, too), and you won’t learn how to think until it’s too late.

Since schools don’t even try to understand the differences between the learning process of children, they never spot this in any child. We only got an early warning from one of the head teachers (the best, so far, at Queen Edith’s), because of behaviour issues, not learning problems. They were simply unaware that our son would not even know why he was right. This is very similar to what expert computer systems can do, and we don’t consider them to be intelligent.

Recently, I took matters into my own hands and am teaching both my kids to think. I don’t care what answer they give me, I want to know why they think that’s the answer. I want explanations, not step-by-step equation solving that can be easily memorised, I want them to tell me why they can apply that step in solving that equation. Why do they think that stars are hotter than planets, why can’t you send messages faster than the speed of light, even with entanglement. Why is what really matters, and that’s the least worry in all schools I’ve ever been, or have ever seen.

Time for a change

Until we manage to find a way to ask why, and get meaningful and measurable answers from our children, we’ll still be in the stone ages. All the progress that we think we’ve made since the wheel is but a fleck on what we can achieve. People that assume our understanding as complete, or even good enough are idiots and should not be given any level of control over our society.

Next time you vote, ask your candidate why, and be ready to change candidates if they don’t understand, or can’t answer the question. You’ll see, like Russel Brand did, that you’ll end up without a candidate.

We need to change how we think, and the question of this century is why?. Ask your kids every day, why. Don’t let them ask why if they can’t answer why. Every day, wake up, look at yourself in the mirror and ask…


Second language curse
December 9th, 2013 under Fun, Life, rengolin. [ Comments: none ]

I count myself privileged of being proficient in a second language (English), which has helped me learn other languages and have a more elastic mind towards different concepts in life. But there is a curse that I just found out, and it turned out to be significant.

For a few years I realised that I was signing my emails with the wrong name: “reanto” instead of “renato“. And since I sign manually all my emails (and I send many emails a day), I could get a true sense of the problem. In the last year or so, the problem got a lot worse, and now I can’t sign my own emails any more without erasing “reanto” and re-writing “renato” almost every time.

Now, misspelling English words (even when you do know the correct spelling) is ok, since I haven’t started typing when we moved to England, far from it. Misspelling Portuguese words is also ok, because the contact with a new language will bring new sounds, and some uncertainty on how to spell a native word will arise after a few years without much contact with it. But misspelling your own name?! That’s a whole new class of fail.

Today it occurred to me that the reason for that might very well be the same as the rest, after all my name is just another word that I know how to spell. And, it turns out that, in the English language, “anis the 5th most common digraph, while “na” doesn’t even register!

So, the frequency which I write the digraphs (and trigraphs) in English are shaping my ability to write my own name. Much the same as the problems that my native language have when I write English, for instance, I have to delete the “e” at the end of many words like “frequent“, as it seems to come before I even think about it.

While writing this small post, the browser’s spell checker has fixed my misspellings (including the previous word) many times, and forcing me to not have the checker bug me, has also forced me to misspell my own name.

The brain is a weird thing…


Tale of The Water
October 20th, 2013 under Digital Rights, Media, Politics, rengolin, Stories. [ Comments: 1 ]

In a village, far from any big city, there lived a family which had access to clean water from a nearby river. With the rain from many spring and autumn months being abundant, the family never had any trouble to wash clothes, cook and drink, or even have a good long bath. But the village, as any good village in the world, grew along that river, and each family had access to clean and fresh water.

As times pass, the legend of good water spread across the land, and more and more people joined the thriving community of the water village. But with growth, there’s lack of space, and not everyone had direct access to the river, but had to cross the original settlers’ gardens to get to water. Some fights and some profits later, the community, that now extended across several rows of houses on both sides of the river, as far as the eye could see, had a meeting to decide what would be done about the “water problem”.

The eldest, and self-elected leader of the community, had many friends among the first settlers. He wasn’t himself living by the river, since he got there not long ago, but with a few favours (especially helping increasing the profits of the original settlers to share their water with the newcomers), he got himself in a pretty good spot, and had enough contacts on both sides of the river to reign almost unimpeded.

To no surprise, he was the first to speak: “Friends of the Water Village, we gather today to decide what to do with the water.” Half-way through the sentence, every body had stopped talking, so he proceeded: “We all know that the water in this village is of the best quality in all the land”, and a chorus in the background said “yeah!”. “We all know that the first settlers have the rights in accessing and distributing the water, which you all know I am not part of, nor I profit from their enterprise, I only help to see that their profits and rights are guaranteed.” There was silence, for most knew that it was a lie, but they either didn’t want to oppose (at least not publicly), or didn’t care.

“But recent events called for a special gathering. So many of you hear that there are people accessing the river via the bridge, which blocks the crossing and put the bridge, which is not of the best quality, in danger!”. “Not to mention that this is a disrespect with the original settlers, that fought so hard to build our thriving community, and gave us the bless of such good water, and have helped us in reaching the water in such beautiful and useful buckets of their own creation.” “We owe them the right to share with us their water, the right to charge for the tireless efforts to provide our homes with the best water, carefully selected and cared for.” There was a faint ovation from the bench where the original settlers were, with many of them only shrugging, or not even that.

“Some of you reported the efforts of our friend that decided to pass a pipe through his land to make it easier to other villagers to have access to water, and that was already dealt with. We destroyed his pipe, and let that be a warning of anyone trying to pervert the art of the original settlers, as we owe them our delicious water!”. “Now, as with any democracy, I open the floor for comments, on how are we going to solve this problems.”

With this, some of the original settlers mentioned how the town should restrict the access to the bridge, and to charge a fee to cross, so that people that uses the bridge have the intention to cross the bridge, not to collect water. Others mentioned that it still wouldn’t stop collectors, but, as some said, they could restrict the validity of the tickets to a short period of time, in which a new charge would be collected.

About the pipe “problem”, many suggested that it should be made illegal to have pipes in any house, not just on the original settles, because connecting pipes between houses was not technically difficult, and it would be hard to solve the problem in case many houses ended up connecting to each other, as it was already happening in the north area.

When all the citizens were heard, and all the votes were taken, most of the ideas were unanimously approved. When the final hammer stroke down, finishing the meeting, one citizen, who was not one of the original settlers rose up: “This is outrageous! It doesn’t make sense, the water comes from the rain, and there is no innate right of the original settlers to charge anything for it!”. As he was saying this, one of the man standing behind the bench left in silence.

To that, not much was done from the central bench, where the eldest was sitting in the middle. He slowly rose is head, adjusted his glasses and smiled. “Friend, we’d be happy to hear your pledge, but as you all know, you don’t have the right to address the council. Only original settlers, and those appointed by them, can speak at the council. If you want to voice your concerns, I suggest you talk to your representative.” To which the man responded: “But my representative is an original settler, and I can’t vote for anyone that is not one, so they don’t represent me, they never had!”. “I’m sorry friend, but this is how democracy works, we can’t change the world just because of you.”.

The villager’s face was red, his eyes twitched slightly. The despair in his mind was clear, but he didn’t have much time to fall into it, for the silent men returned to the settlers’ bench and whispered something to the eldest’s ear only. The eldest turned his head again to the nonconformist villager. “Dear sir, we hear stories that you have been consistently using the bridge in the past days, is that true?”. “Well, yes, my sister lives on the other side, and I go visit her every day.”. “The reports also say that you take a bucket with you, and that you fill it with water, do you agree?”. “Well, yes, of course, I take the water for my sick sister, she needs it to aid her recovery.”. “And you haven’t paid a single settler for more than a month, how much water do you have stored at your house, dear sir?”.

It didn’t take long for the strong men behind the bench take the poor villager into a closed room, and he was never heard of ever again. Even though the water is a resource from nature, and despite the fact that water is essential to every living creature, the innate right of ownership of basic needs is common place in many parts of the world.

Creativity is a gift we received from evolution, as a way to save ourselves from more powerful foes. Creativity has a large proportion of imitation, since other living beings have different ideas, equally effective, against our common foes, and those that copy and share ideas, survive for longer. And yet, out society believes, for some serious distortion of natural reality, that the right to own something is more important than the right to survive.

If you read this story again, but replacing “water” with “music”, and making the appropriate changes, you’ll see that it makes as much sense as the original tale. And yet, a huge empire is built on the presumption that creativity can be owned by anyone. Who was the first to play certain tune? How many completely separate cultures have the same beat on their millenarian songs? There are infinite ways of combining words, but only a few actually make sense, and a lot less than that ends up beautiful.

Songs, poems, tales, videos, films, theatre are all forms of expressing the same feelings in different ways, but some people have the luxury of owning the rights of a particular way of expression, mainly because the law is written to favour them, than because they have actually created something truly new. No one has.

We all copy ideas. That’s called survival. That’s genetic. That’s what define us.

Why are we so ashamed of our own past? Why do we accept that the rich gets richer on our own account? Why do we agree that paying millions of dollars to an already filthy rich actors, directors and producers makes sense, for them to give us the benefit of watching the “Hangover III”, when it’s an absolute copy of itself for the second time, when the original was a pout-pourri of many other films and stories? Why do we accept a law that makes us criminals by sharing creativity, a basic instinct of the human race?

What has come of the human race to accept this as “normal”?

Open Source and Profit
July 8th, 2013 under Corporate, Devel, Digital Rights, OSS, rengolin, World. [ Comments: 2 ]

I have written extensively about free, open source software as a way of life, and now reading back my own articles of the past 7 years, I realize that I was wrong on some of the ideas, or in the state of the open source culture within business and around companies.

I’ll make a bold statement to start, trying to get you interested in reading past the introduction, and I hope to give you enough arguments to prove I’m right. Feel free to disagree on the comments section.

The future of business and profit, in years to come, can only come if surrounded by free thoughts.

By free thoughts I mean free/open source software, open hardware, open standards, free knowledge (both free as in beer and as in speech), etc.

Past Ideas

I began my quest to understand the open source business model back in 2006, when I wrote that open source was not just software, but also speech. Having open source (free) software is not enough when the reasons why the software is free are not clear. The reason why this is so is that the synergy, that is greater than the sum of the individual parts, can only be achieved if people have the rights (and incentives) to reach out on every possible level, not just the source, or the hardware. I make that clear later on, in 2009, when I expose the problems of writing closed source software: there is no ecosystem in which to rely, so progress is limited and the end result is always less efficient, since the costs to make it as efficient are too great and would drive the prices of the software too high up to be profitable.

In 2008 I saw both sides of the story, pro and against Richard Stallman, on the views of the legitimacy of propriety control, being it via copyright licenses or proprietary software. I may have come a long way, but I was never against his idea of the perfect society, Richard Stallman’s utopia, or as some friends put it: The Star Trek Universe. The main difference between me and Stallman is that he believes we should fight to the last man to protect ourselves from the evil corporations towards software abuse, while I still believe that it’s impossible for them to sustain this empire for too long. His utopia will come, whether they like it or not.

Finally, in 2011 I wrote about how copying (and even stealing) is the only business model that makes sense (Microsoft, Apple, Oracle etc are all thieves, in that sense) and the number of patent disputes and copyright infringement should serve to prove me right. Last year I think I had finally hit the epiphany, when I discussed all these ideas with a friend and came to the conclusion that I don’t want to live in a world where it’s not possible to copy, share, derive or distribute freely. Without the freedom to share, our hands will be tied to defend against oppression, and it might just be a coincidence, but in the last decade we’ve seen the biggest growth of both disproportionate propriety protection and disproportional governmental oppression that the free world has ever seen.

Can it be different?

Stallman’s argument is that we should fiercely protect ourselves against oppression, and I agree, but after being around business and free software for nearly 20 years, I so far failed to see a business model in which starting everything from scratch, in a secret lab, and releasing the product ready for consumption makes any sense. My view is that society does partake in an evolutionary process that is ubiquitous and compulsory, in which it strives to reduce the cost of the whole process, towards stability (even if local), as much as any other biological, chemical or physical system we know.

So, to prove my argument that an open society is not just desirable, but the only final solution, all I need to do is to show that this is the least energy state of the social system. Open source software, open hardware and all systems where sharing is at the core should be, then, the least costly business models, so to force virtually all companies in the world to follow suit, and create the Stallman’s utopia as a result of the natural stability, not a forced state.

This is crucial, because every forced state is non-natural by definition, and every non-natural state has to be maintained by using resources that could be used otherwise, to enhance the quality of the lives of the individuals of the system (being them human or not, let’s not block our point of view this early). To achieve balance on a social system we have to let things go awry for a while, so that the arguments against such a state are perfectly clear to everyone involved, and there remains no argument that the current state is non-optimal. If there isn’t discomfort, there isn’t the need for change. Without death, there is no life.


Of all the bad ideas us humans had on how to build a social system, capitalism is probably one of the worst, but it’s also one of the most stable, and that’s because it’s the closest to the jungle rule, survival of the fittest and all that. Regulations and governments never came to actually protect the people, but as to protect capitalism from itself, and continue increasing the profit of the profitable. Socialism and anarchy rely too much on forced states, in which individuals have to be devoid of selfishness, a state that doesn’t exist on the current form of human beings. So, while they’re the product of amazing analysis of the social structure, they still need heavy genetic changes in the constituents of the system to work properly, on a stable, least-energy state.

Having less angry people on the streets is more profitable for the government (less costs with security, more international trust in the local currency, more investments, etc), so panis et circenses will always be more profitable than any real change. However, with more educated societies, result from the increase in profits of the middle class, more real changes will have to be made by governments, even if wrapped in complete populist crap. One step at a time, the population will get more educated, and you’ll end up with more substance and less wrapping.

So, in the end, it’s all about profit. If not using open source/hardware means things will cost more, the tendency will be to use it. And the more everyone uses it, the less valuable will be the products that are not using it, because the ecosystem in which applications and devices are immersed in, becomes the biggest selling point of any product. Would you buy a Blackberry Application, or an Android Application? Today, the answer is close to 80% on the latter, and that’s only because they don’t use the former at all.

It’s not just more expensive to build Blackberry applications, because the system is less open, the tools less advanced, but also the profit margins are smaller, and the return on investment will never justify. This is why Nokia died with their own App store, Symbian was not free, and there was a better, free and open ecosystem already in place. The battle had already been lost, even before it started.

But none of that was really due to moral standards, or Stallman’s bickering. It was only about profit. Microsoft dominated the desktop for a few years, long enough to make a stand and still be dominant after 15 years of irrelevance, but that was only because there was nothing better when they started, not by a long distance. However, when they tried to flood the server market, Linux was not only already relevant, but it was better, cheaper and freer. The LAMP stack was already good enough, and the ecosystem was so open, that it was impossible for anyone with a closed development cycle to even begin to compete on the same level.

Linux became so powerful that, when Apple re-defined the concept of smartphones with the iPhone (beating Nokia’s earlier attempts by light-years of quality), the Android system was created, evolved and dominated in less than a decade. The power to share made possible for Google, a non-device, non-mobile company, to completely outperform a hardware manufacturer in a matter of years. If Google had invented a new OS, not based on anything existent, or if they had closed the source, like Apple did with FreeBSD, they wouldn’t be able to compete, and Apple would still be dominant.

Do we need profit?

So, the question is: is this really necessary? Do we really depend on Google (specifically) to free us from the hands of tyrant companies? Not really. If it wasn’t Google, it’d be someone else. Apple, for a long time, was the odd guy in the room, and they have created an immense value for society: they gave us something to look for, they have educated the world on what we should strive for mobile devices. But once that’s done, the shareable ecosystem learns, evolves and dominate. That’s not because Google is less evil than Apple, but because Android is more profitable than iOS.

Profit here is not just the return on investment that you plan on having on a specific number of years, but adding to that, the potential that the evolving ecosystem will allow people to do when you’ve long lost the control over it. Shareable systems, including open hardware and software, allow people far down in the planing, manufacturing and distributing process to still have profit, regardless of what were your original intentions. One such case is Maddog’s Project Cauã.

By using inexpensive RaspberryPis, by fostering local development and production and by enabling the local community to use all that as a way of living, Maddog’s project is using the power of the open source initiative by completely unrelated people, to empower the people of a country that much needs empowering. That new class of people, from this and other projects, is what is educating the population of the world, and what is allowing the people to fight for their rights, and is the reason why so many civil uprisings are happening in Brazil, Turkey, Egypt.


All that creates instability, social unrest, whistle-blowing gone wrong (Assange, Snowden), and this is a good thing. We need more of it.

It’s only when people feel uncomfortable with how the governments treat them that they’ll get up their chairs and demand for a change. It’s only when people are educated that they realise that oppression is happening (since there is a force driving us away from the least-energy state, towards enriching the rich), and it’s only when these states are reached that real changes happen.

The more educated society is, the quicker people will rise to arms against oppression, and the closer we’ll be to Stallman’s utopia. So, whether governments and the billionaire minority likes or not, society will go towards stability, and that stability will migrate to local minima. People will rest, and oppression will grow in an oscillatory manner until unrest happens again, and will throw us into yet another minimum state.

Since we don’t want to stay in a local minima, we want to find the best solution not just a solution, having it close to perfect in the first attempt is not optimal, but whether we get it close in the first time or not, the oscillatory nature of social unrest will not change, and nature will always find a way to get us closer to the global minimum.


Is it possible to stay in this unstable state for too long? I don’t think so. But it’s not going to be a quick transition, nor is it going to be easy, nor we’ll get it on the first attempt.

But more importantly, reaching stability is not a matter of forcing us to move towards a better society, it’s a matter of how dynamic systems behave when there are clear energetic state functions. In physical and chemical systems, this is just energy, in biological systems this is the propagation ability, and in social systems, this is profit. As sad as it sounds…

Amazon loves to annoy
June 27th, 2013 under Digital Rights, Gadgtes, rengolin, Software, Unix/Linux, Web. [ Comments: none ]

It’s amazing how Amazon will do all in their power to annoy you. They will sell you DRM-free MP3 songs, and even allow you to download on any device (via their web interface) the full version, for your own personal use, in the car, at home or when mobile. But, not without a cost, no.

For some reason, they want to have total control of the process, so if they’ll allow you to download your music, it has to be their way. In the past, you had to download the song immediately after buying, with a Windows-only binary (why?) and you had only one shot. If the link failed, you just lost a couple of pounds. To be honest, that happened to me, and customer service were glad to re-activate my “license” so I could download it again. Kudos for that.

Question 1: Why did they need an external software to download the songs when they had a full-featured on-line e-commerce solution?

It’s not hard to sell on-line music, other people have been doing it for years and not in that way, for sure. Why was it so hard for Amazon, the biggest e-commerce website on Earth, to do the same? I was not asking for them to revolutionise the music industry (I leave that for Spotify), just do what others were doing at the time. Apparently, they just couldn’t.

Recently, it got a lot better, and that’s why I started buying MP3 songs from Amazon. They now had a full-featured MP3 player on the web! They also have the Android version of it that is a little confusing but unobtrusive. The web version is great, once you buy an album you go directly to it and you can already start listening to songs and all.

Well, I’m a control freak, and I want to have all songs I own on my own server (and its backup), so I went to download my recently purchased songs. Well, it’s not that simple: you can download all your songs, on Windows and Mac… not Linux.

Question 2: Why on Earth can’t they make it work on Linux?

We’re not talking about Microsoft or Apple. This is Amazon, a web company that is supposed to know how JavaScript works, right? Why create executables, ActiveX, SilverLight or whatever those platforms demand from their developers when they can do the same just using JavaScript? The era when JavaScript was too slow and Flash rocked is over, like, 10 years ago. There simply is no excuse.

Undeterred, I knew the Android app would let me download, and as an added bonus, all songs downloaded by AmazonMP3 would be automatically added to the Android music playlists, so that both programs could play the same songs. That was great, of course, until I wanted to copy them to my laptop.

When running (the fantastic) ES File Explorer, I listed the folders consuming most of the SDCARD, found the amazonmp3 folder and saw that all my songs were in there. Since Android changed the file-system, and I can’t seem to mount it correctly via MTP (noob), I decided to use the ES File Explorer (again) to select all files and copy to my server via its own interface, that is great for that sort of thing, and well, found out that it’s not that simple. Again.

Question 3: Why can I read and delete the songs, but not copy them?

What magic Linux permission let me listen to a song (read) and delete the file (write) but not copy to another location? I can’t think of a way to natively do that on Linux, it must be a magic from Android, to allow for DRM crap.

At this time I was already getting nervous, so I just fired adb shell and navigated to the directory, and when I listed the files, adb just logged out. I tried again, and it just exited. No error message, no log, no warning, just shut down and get me back to my own prompt.

This was getting silly, but I had the directory, so I just ran adb pull /sdcard/amazonmp3/ and found that only the temp directory came out. What the hell is this sorcery?!

Question 4: What kind of magic stops me from copying files, or even listing files from a shell?

Well, I knew it was something to do with the Amazon MP3 application itself, if couldn’t be something embedded on Android, or the activists would crack on until they ceded, or at least provided means for disabling DRM crap from the core. To prove my theory, I removed the AmazonMP3 application and, as expected, I could copy all my files via adb to my server, where I could then, back them up.

So, if you use Linux and want to download all your songs from Amazon MP3 website, you’ll have to:

  1. Buy songs/albuns on Amazon’s website
  2. Download them via AmazonMP3 Android app (click on album, click on download)
  3. Un-install the AmazonMP3 app
  4. Get the files via: adb pull /sdcard/amazonmp3/
  5. Re-install the AmazonMP3 app (if you want, or to download more songs)

As usual, Amazon was a pain in the back with what should be really, really simple for them to do. And, as usual, a casual user finds its way to getting what they want, what they paid for, what they deserve.

If you know someone at Amazon, please let them know:

We’re not idiots. We know you know JavaScript, we know you use Linux, and we know you can create an amazing experience for all of us. Don’t treat us like idiots. If your creativity is lacking, just copy the design and implementation from someone else, we don’t care. We want solutions, not problems.

Game Theory and the fate of a generation
May 24th, 2013 under Life, rengolin. [ Comments: none ]

An interesting though came up via Bruce Schneier’s blog that got me thinking, and having trouble educating my pre-teen child, that thought grew on me and now many of his behaviours can be explained by the inability of spotting which game to play in real life.

When I finally had this same conversation with him, a whole model of how much of a failure our society is becoming, appeared clear as day for both of us!

What games do we play?

First, a crash course on game theory, you can skip this part if you already know. Basically, a game is played between two players who can take decisions based on what they think the other player will do, and points are given whether you cooperate or not in conjunction with the other players cooperation or not. For example, if both cooperate, both get 5 points. If one cooperates and the other doesn’t, the cheater gets 7 points and the looser gets 0. If they’re both cheaters, both get 1 point.

Well, since you have no idea what the other will choose, there’s 50% chance that the other player will cooperate and 50% that she will not. If you choose to cooperate, you have 50% chance of getting 5 points and 50% of getting zero. If you don’t, it’s 50% 7 points and 50% 1 point.

Clearly, if you play the game only once, cheating is the answer. There is no reason not to cheat. However, if you’ll have to play the same game with the same player more than once, possibly your whole life, than, well, cheating tires quickly. If you cheat now, the other player will cheat next, and both of you will remain cheating forever, since you know that if you don’t, by definition, you’ll get 0 points and she will get 7. We call this a stable solution, once you get there, there’s no coming back.

However, if both cooperate, both get 5, and as long as you both cooperate, you’ll always get 5. Sure, it’s not as profitable as 7, but it’s close enough. But as soon as one cheats, the other will feel betrayed, and will cheat. We call this an unstable solution. It demands trust on the other player, and as soon as the trust is broken, it’ll be very hard to regain it.

If that made you think about how life treats you, it’s no coincidence. John Nash used that language to describe reality, and he could clearly see reality like better than most of us. When John Nash says that “life is a game”, he truly means it, and he came up with the mathematical notation to prove it, and studied it to great length.

Video Games

In the beginning, there was pong. Pong was simple and fun. Then, the explosion of video games in the 80′s brought a lot of easy and hard games, but in almost all of them you had to work hard to get the prize. Some of then didn’t even had a prize, it was just an infinite number of repetitions, faster and faster, and the real competition was among the players, who got the best score.

The real game, however, was not on the screen, was on the player’s brain. Those games have conditioned people that there is a prize, and there is a task, and they are related. If they perform the task better than a certain threshold, the prize is bronze/silver/gold. It feels really good to get a prize, and that way of making people feel good (or bad) was found a century ago by Ivan Pavlov.

But video games is as much Pavlovian as street games. They’re as innocent and as powerful as any Olympic game on the minds of people. Video games use a different part of the body, the brain, and for that it was much more popular amongst nerds than sporty types. They had found a niche, at least before the 90′s arrived, when a boom of consoles, PCs and 3D graphics made video games mainstream, with every house having at least one type of video game.

That boom had little change in the shape of how the games were teaching children about the world. There was still a task, a reward, and some work to do. Even though, by the end of the day, any task you performed during the game was worthless in real life, what you learnt, that is that you need to perform a task well enough to get a prize, and that the prize is proportional to the hard work you put in, was learnt for life.

Social Gaming

Enter the era of social gaming. Zynga and other Facebook games were made not to entertain, or to give prizes for specific tasks, but to reward the most socially active player. All that, of course, in order to give Facebook a boost in user numbers (and Zynga a boost in fake value), but that not only changed how games were played, but it changed the lessons that we learnt from them.

On a social game, since the objective is to share more than others, you’ll get things for free to share with your friends, who would also get free stuff to share with you. It means that, whoever got the most “friends”, got most free stuff, and progressed faster and longer in the game. What it’s teaching you is that you don’t need to work hard for something, you just need to convince people to give you for free, or even worse, you just need to wait to get it, because it’s the player’s right to receive.

Now, what children are learning with these games is that they don’t need to work hard for anything, because they have the right to be happy, the right to be fed, the right to be given jobs, or be subsided by the government.

If that sounds a lot like reality, well, welcome to the brave new world!


So, we know how powerful Facebook is, and much of that came from the games section at the beginning, that forced people to spend more time on Facebook than on real life, and now it’s just an addiction that they cannot get free. The reason why it’s an addiction is the very same why Heroine is an addiction.

Whenever you use a psychotropic drug, your brain goes to a state that is not real. Whatever you feel, whatever you see is not real. You can see good things, or bad things, and that will change how your addiction will continue, but some drugs are more powerful that that. For instance, tobacco changes the concentration that your brain and peripheral nervous system respond to neurotransmitters, and that’s because nicotine is a joker in the land of neurotransmitters. It can trigger more than half of the different types of receptors in your body. Whenever you lower that concentration (by abstaining), your body doesn’t react like you would want, and you have withdraw, which compels you to smoke again.

Most drugs have the same effect, including easy over-rewarding video games. Note that not all video games act like drugs, it’s just the specific class of games where you get more than what you deserve for the amount of work you put in. And that’s the same kind of addiction that people have with films, series, books and anything that will take you away from the harsh reality into a land of dreams where you are more than you can actually accomplish (super hero) or you have accomplished more than you actually worked for it (fantasy and feel-good stories).

The crucial bit here is that, going back to reality is hard, painful and has a deep feeling of loss, since all the “hard work” you put during the game/film/book is gone and worthless. That feeling puts you into a dilemma: now that you lost a lot of time in reality that you could be doing something useful, while other people are already harvesting the fruits of their own works (a younger child playing piano or solving puzzles you cannot), you’ll have to work much harder to achieve the same level. Whereas, if you go back to the game, you’ll get instant satisfaction with very little effort. If you have no responsibilities in your life, the choice is easy.


This creates a conflict with the parents because, not only they had to work hard for upbringing their children on the best environment possible, but they’re also seeing their children wast their time on a false reality while not understanding why the parent’s reality is so different from their own.

I played video games since I was very young and still play them constantly, but I simply cannot play social games. They feel wrong, false and demeaning of the very hard work that I learnt as a kid to foster. Moreover, they remind me of the kind of society we live today where children can’t fail.

For example, in Brazil, not enough people were reaching universities because they would fail so many times that they’d drop school and never bother. How do you fix this? Simple, make a law where kids younger than 10 cannot fail. Ever. Well, surprise, they reached 10 without being able to read or write, and that’s the state’s fault, so how do you fix this? Even simpler, pass a law where kids under 15 cannot fail. You get the idea.

This over protection that schools have on kids, society trying to avoid the problems of growing up and taking responsibility until very late, is possibly responsible for the increase in criminality of the new youth and the will of some people to reduce the criminal age to 16. It’s not hard to see that, again, that solution is only going to make things worse by treating children like adults without given them a chance to understand adulthood before it’s too late.

Game playing society

Since social gaming became so mainstream a few years ago, people started noticing how to use that for benefit and profit. Real life games, like fourSquare give you prizes for over-consumption, on the grounds that sharing your personal information is worthless for you, but not for them. Games where you feel you’re giving a worthless commodity (your privacy) for big rewards (a cup of coffee) but in reality the companies are getting the real profit (your private information) is where our society is leading and it doesn’t seem to bother many people.

We are already brainwashed to believe that sharing personal emails with Google is ok, as long as they keep the servers up. We put our credit card numbers on Amazon for the comfort of not having to type them so often on the trust that they will protect your data as if it was their own. We already believe that the cloud is the best place to store your photos, documents and music. While all of that looks free to you, it’s far from. It’s all a game, where you are being cheated while willingly cooperating, but they keep your profit positive (albeit small), so that you feel valued.

We already let our guard down, we’re living in that fantasy where we don’t have to work hard for anything, convinced ourselves that the profit is ours and in this fantasy world, we’re great. Easy pray to an ever relaxing predators. Maybe that will be the end of them… I hope.

Playing the wrong game

Now we pause to go back to the main theme: why people play a one-off game when they should actually play a rolling game?

100 years ago, justice wasn’t very just. Judge and executioner were often the same person, and people paid a lot more than they should for crimes that they may have not even committed. But as bad as it was, that taught a lesson to most people that the odds of cheating weren’t that great. The price was too high, and they’d see it far too often.

Years pass, people agree that totalitarian regimes are not nice and we come with democracy, republics and other less radical governments. Now, people have rights, inalienable and universal. Governments have to protect people, and people can now be what they want, follow their dreams and collect the fruits of their hard work. And the more educated people get, the more they realise they can get more rights.

In itself, having rights is the right thing to do (pun intended), but there has to be a balance, and the balance is the social interactions. Your rights are the same as everyone else, and you can’t just do what you “want”, but what you have the right to do. Well, clever people can turn those concepts around and they will cheat, and they will profit. Because they have to be protected by law, they will find ways of abusing the system short of breaking the law. If they get caught, the price is high, but since they have more rights than duties, and since justice is less impressive (but more just) nowadays, the feeling of cost and profits are skewed, so people cheat more often that they would if thinking straight.

We can’t have the concept of born rights without having the concept of born duties. You have the right to education, but you also have the duty to follow it through, no matter how hard it seems. It’s the teachers’ duty to do their best to make it more efficient (not easier), but it’s also their right to chose what they think it’s best for the kids. If rights and duty don’t go hand-in-hand, you get a lazy generation that thinks other people have to do whatever they want. Today, children will think that of their parents, what about tomorrow? Will they expect that their children will have to work for them? Or their brothers? It doesn’t add up. They’re not playing a rolling game, but a one-off one.

When you thrown the over-rewarding games into the mix, you get kids learning that they can just be lazy and the world will fix it for them while they get cheap happiness on their tablets. They’re cheating the system that protects them until they turn 18 when the system will just abandon them, and the hard reality will hit them in the face with no preparedness and no warning. Some survive, some don’t. Would you take a chance with your children?

Uno score keeper
March 31st, 2013 under Devel, OSS, rengolin, Software. [ Comments: none ]

With the spring not coming soon, we had to improvise during the Easter break and play Uno every night. It’s a lot of fun, but it can take quite a while to find a piece of clean paper and a pen that works around the house, so I wondered if there was an app for that. It turns out, there wasn’t!

There were several apps to keep card game scores, but every one was specific to the game, and they had ads, and wanted access to the Internet, so I decided it was worth it writing one myself. Plus, that would finally teach me to write Android apps, a thing I was delaying to get started for years.

The App

Adding new players

Card Game Scores

The app is not just a Uno score keeper, it’s actually pretty generic. You just keep adding points until someone passes the threshold, when the poor soul will be declared a winner or a loser, depending on how you set up the game. Since we’re playing every night, even the 30 seconds I spent re-writing our names was adding up, so I made it to save the last game in the Android tuple store, so you can retrieve it via the “Last Game” button.

It’s also surprisingly easy to use (I had no idea), but if you go back and forth inside the app, it cleans the game and start over a new one, with the same players, so you can go on as many rounds as you want. I might add a button to restart (or leave the app) when there’s a winner, though.

I’m also thinking about printing the names in order in the end (from victorious to loser), and some other small changes, but the way it is, is good enough to advertise and see what people think.

If you end up using, please let me know!

Download and Source Code

The app is open source (GPL), so rest assured it has no tricks or money involved. Feel free to download it from here, and get the source code at GitHub.

Distributed Compilation on a Pandaboard Cluster
February 13th, 2013 under Devel, Distributed, OSS, rengolin. [ Comments: 2 ]

This week I was experimenting with the distcc and Ninja on a Pandaboard cluster and it behaves exactly as I expected, which is a good thing, but it might not be what I was looking for, which is not. ;)

Long story short, our LLVM buildbots were running very slow, from 3 to 4.5 hours to compile and test LLVM. If you consider that at peak time (PST hours) there are up to 10 commits in a single hour, the buildbot will end up testing 20-odd patches at the same time. If it breaks in unexpected ways, of if there is more than one patch on a given area, it might be hard to spot the guilty.

We ended up just avoiding the make clean step, which put us around 15 minutes build+tests, with the odd chance of getting 1 or 2 hours tops, which is a great deal. But one of the alternatives I was investigating is to do a distributed build. More so because of the availability of cluster nodes with dozens of ARM cores inside, we could make use of such a cluster to speed up our native testing, even benchmarking on a distributed way. If we do it often enough, the sample might be big enough to account for the differences.

The cluster

So, I got three Pandaboards ES (dual Cortex-A9, 1GB RAM each) and put the stock Ubuntu 12.04 on them and installed the bare minimum (vim, build-essential, python-dev, etc), upgraded to the latest packages and they were all set. Then, I needed to find the right tools to get a distributed build going.

It took a bit of searching, but I ended up with the following tool-set:

  • distcc: The distributed build dispatcher, which knows about the other machines in the cluster and how to send them jobs and get the results back
  • CMake: A Makefile generator which LLVM can use, and it’s much better than autoconf, but can also generate Ninja files!
  • Ninja: The new intelligent builder which not only is faster to resolve dependencies, but also has a very easy way to change the rules to use distcc, and also has a magical new feature called pools, which allow me to scale job types independently (compilers, linkers, etc).

All three tools had to be compiled from source. Distcc’s binary distribution for ARM is too old, CMake’s version on that Ubuntu couldn’t generate Ninja files and Ninja doesn’t have binary distributions, full stop. However, it was very simple to get them interoperating nicely (follow the instructions).

You don’t have to use CMake, there are other tools that generate Ninja files, but since LLVM uses CMake, I didn’t have to do anything. What you don’t want is to generate the Ninja files yourself, it’s just not worth it. Different than Make, Ninja doesn’t try to search for patterns and possibilities (this is why it’s fast), so you have to be very specific on the Ninja file on what you want to accomplish. This is very easy for a program to do (like CMake), but very hard and error prone for a human (like me).


To use distcc is simple:

  1. Replace the compiler command by distcc compiler on your Ninja rules;
  2. Set the environment variable DISTCC_HOSTS to the list of IPs that will be the slaves (including localhost);
  3. Start the distcc daemon on all slaves (not on the master): distccd --daemon --allow <MasterIP>;
  4. Run ninja with the number of CPUs of all machines + 1 for each machine. Ex: ninja -j6 for 2 Pandaboards.

A local build, on a single Pandaboard of just LLVM (no Clang, no check-all) takes about 63 minutes. With distcc and 2 Pandas it took 62 minutes!

That’s better, but not as much as one would hope for, and the reason is a bit obvious, but no less damaging: The Linker! It took 20 minutes to compile all of the code, and 40 minutes to link them into executable. That happened because while we had 3 compilation jobs on each machine, we had 6 linking jobs on a single Panda!

See, distcc can spread the compilation jobs as long as it copies the objects back to the master, but because a linker needs all objects in memory to do the linking, it can’t do that over the network. What distcc could do, with Ninja’s help, is to know which objects will be linked together, and keep copies of them on different machines, so that you can link on separate machines, but that is not a trivial task, and relies on an interoperation level between the tools that they’re not designed to accept.

Ninja Pools

And that’s where Ninja proved to be worth its name: Ninja pools! In Ninja, pools are named resources that bundle together with a specific level of scalability. You can say that compilers scale free, but linkers can’t run more than a handful. You simply need to create a pool called linker_pool (or anything you want), give it a depth of, say, 2, and annotate all linking jobs with that pool. See the manual for more details.

With the pools enabled, a distcc build on 2 Pandaboards took exactly 40 minutes. That’s 33% of gain with double the resources, not bad. But, how does that scale if we add more Pandas?

How does it scale?

To get a third point (and be able to apply a curve fit), I’ve added another Panda and ran again, with 9 jobs and linker pool at 2, and it finished in 30 minutes. That’s less than half the time with three times more resources. As expected, it’s flattening out, but how much more can we add to be profitable?

I don’t have an infinite number of Pandas (nor I want to spend all my time on it), so I just cheated and got a curve fitting program (xcrvfit, in case you’re wondering) and cooked up an exponential that was close enough to the points and use the software ability to do a best fit. It came out with 86.806*exp(-0.58505*x) + 14.229, which according to Lybniz, flattens out after 4 boards (about 20 minutes).

Pump Mode

Distcc has a special mode called pump mode, in which it pushes with the C file, all headers necessary to compile it solely on the node. Normally, distcc will pre-compile on the master node and send the pre-compiled result to the slaves, which convert to object code. According to the manual, this could improve the performance 10-fold! Well, my results were a little less impressive, actually, my 3-Panda cluster finished in just about 34 minutes, 4 minutes more than without push mode, which is puzzling.

I could clearly see that the files were being compiled in the slaves (distccmon-text would tell me that, while there was a lot of “preprocessing” jobs on the master before), but Ninja doesn’t print times on each output line for me to guess what could have slowed it down. I don’t think there was any effect on the linker process, which was still enabled in this mode.


Simply put, both distcc and Ninja pools have shown to be worthy tools. On slow hardware, such as the Pandas, distributed builds can be an option, as long as you have a good balance between compilation and linking. Ninja could be improved to help distcc to link on remote nodes as well, but that’s a wish I would not press on the team.

However, scaling only to 4 boards will reduce a lot of the value for me, since I was expecting to use 16/32 cores. The main problem is again the linker jobs working solely on the master node, and LLVM having lots and lots of libraries and binaries. Ninja’s pools can also work well when compiling LLVM+Clang on debug mode, since the objects are many times bigger, and even on above average machine you can start swapping or even freeze your machine if using other GUI programs (browsers, editors, etc).

In a nutshell, the technology is great and works as advertised, but with LLVM it might not be yet the thing. It’s still more profitable to get faster hardware, like the Chromebooks, that are 3x faster than the Pandas and cost only marginally more.

Would also be good to know why the pump mode has regressed in performance, but I have no more time to spend on this, so I leave as a exercise to the reader. ;)

LLVM Vectorizer
February 12th, 2013 under Algorithms, Devel, rengolin. [ Comments: 2 ]

Now that I’m back working full-time with LLVM, it’s time to get some numbers about performance on ARM.

I’ve been digging the new LLVM loop vectorizer and I have to say, I’m impressed. The code is well structured, extensible and above all, sensible. There are lots of room for improvement, and the code is simple enough so you can do it without destroying the rest or having to re-design everything.

The main idea is that the loop vectorizer is a Loop Pass, which means that if you register this pass (automatically on -O3, or with -loop-vectorize option), the Pass Manager will run its runOnLoop(Loop*) function on every loop it finds.

The three main components are:

  1. The Loop Vectorization Legality: Basically identifies if it’s legal (not just possible) to vectorize. This includes checking if we’re dealing with an inner loop, and if it’s big enough to be worth, and making sure there aren’t any conditions that forbid vectorization, such as overlaps between reads and writes or instructions that don’t have a vector counter-part on a specific architecture. If nothing is found to be wrong, we proceed to the second phase:
  2. The Loop Vectorization Cost Model: This step will evaluate both versions of the code: scalar and vector. Since each architecture has its own vector model, it’s not possible to create a common model for all platforms, and in most cases, it’s the special behaviour that makes vectorization profitable (like 256-bits operations in AVX), so we need a bunch of cost model tables that we consult given an instruction and the types involved. Also, this model doesn’t know how the compiler will lower the scalar or vectorized instructions, so it’s mostly guess-work. If the vector cost (normalized to the vector size) is less than the scalar cost, we do:
  3. The Loop Vectorization: Which is the proper vectorization, ie. walking through the scalar basic blocks, changing the induction range and increment, creating the prologue and epilogue, promote all types to vector types and change all instructions to vector instructions, taking care to leave the interaction with the scalar registers intact. This last part is a dangerous one, since we can end up creating a lot of copies from scalar to vector registers, which is quite expensive and was not accounted for in the cost model (remember, the cost model is guess-work based).

All that happens on a new loop place-holder, and if all is well at the end, we replace the original basic blocks by the new vectorized ones.

So, the question is, how good is this? Well, depending on the problems we’re dealing with, vectorizers can considerably speed up execution. Especially iterative algorithms, with lots of loops, like matrix manipulation, linear algebra, cryptography, compression, etc. In more practical terms, anything to do with encoding and decoding media (watching or recording videos, pictures, audio), Internet telephones (compression and encryption of audio and video), and all kinds of scientific computing.

One important benchmark for that kind of workload is Linpack. Not only Linpack has many examples of loops waiting to be vectorized, but it’s also the benchmark that defines the Top500 list, which classifies the fastest computers in the world.


So, both GCC and Clang now have the vectorizers turned on by default with -O3, so comparing them is as simple as compiling the programs and see them fly. But, since I’m also interested in seeing what is the performance gain with just the LLVM vectorizer, I also disabled it and ran a clang with only  -O3, no vectorizer.

On x86_64 Intel (Core i7-3632QM), I got these results:

Compiler Opt Avg. MFLOPS Diff
Clang -O3 2413 0.0%
GCC -O3 vectorize 2421 0.3%
Clang -O3 vectorize 3346 38.6%

This is some statement! The GCC vectorizer exists for a lot longer than LLVM’s and has been developed by many vectorization gurus and LLVM seems to easily beat GCC in that field. But, a word of warning, Linpack is by no means representative of all use cases and user visible behaviour, and it’s very likely that GCC will beat LLVM on most other cases. Still, a reason to celebrate, I think.

This boost mean that, for many cases, not only the legality if the transformations are legal and correct (or Linpack would have gotten wrong results), but they also manage to generate faster code at no discernible cost. Of course, the theoretical limit is around 4x boost (if you manage to duplicate every single scalar instruction by a vector one and the CPU has the same behaviour about branch prediction and cache, etc), so one could expect a slightly higher number, something on the order of 2x better.

It depends on the computation density we’re talking about. Linpack tests specifically the inner loops of matrix manipulation, so I’d expect a much higher ratio of improvement, something around 3x or even closer to 4x. VoIP calls, watching films and listening to MP3 are also good examples of densely packet computation, but since we’re usually running those application on a multi-task operating system, you’ll rarely see improvements higher than 2x. But general applications rarely spend that much time on inner loops (mostly waiting for user input and then doing a bunch of unrelated operations, hardly vectorizeable).

Another important aspect of vectorization is that it saves a lot of battery juice. MP3 decoding doesn’t really matter if you finish in 10 or 5 seconds, as long as the music doesn’t stop to buffer. But taking 5 seconds instead of 10 means that on the other 5 seconds the CPU can reduce its voltage and save battery. This is especially important in mobile devices.

What about ARM code?

Now that we know the vectorizer works well, and the cost model is reasonably accurate, how does it compare on ARM CPUs?

It seems that the grass is not so green on this side, at least not at the moment. I have reports that on ARM it also reached the 40% boost similar to Intel, but what I saw was a different picture altogether.

On a Samsung Chromebook (Cortex-A15) I got:

Compiler Opt Avg. MFLOPS Diff
Clang -O3 796 0.0%
GCC -O3 vectorize 736 -8.5%
Clang -O3 vectorize 773 -2.9%

The performance regression can be explained by the amount of scalar code intermixed with vector code inside the inner loops as a result of shuffles (movement of data within the vector registers and between scalar and vector registers) not being lowered correctly. This most likely happens because the LLVM back-end relies a lot on pattern-matching for instruction selection (a good thing), but the vectorizers might not be producing the shuffles in the right pattern, as expected by each back-end.

This can be fixed by tweaking the cost model to penalize shuffles, but it’d be good to see if those shuffles aren’t just mismatched against the patterns that the back-end is expecting. We will investigate and report back.


Got results for single precision floating point, which show a greater improvement on both Intel and ARM.

On x86_64 Intel (Core i7-3632QM), I got these results:

Compiler Opt Avg. MFLOPS Diff
Clang -O3 2530 0.0%
GCC -O3 vectorize 3484 37.7%
Clang -O3 vectorize 3996 57.9%

On a Samsung Chromebook (Cortex-A15) I got:

Compiler Opt Avg. MFLOPS Diff
Clang -O3 867 0.0%
GCC -O3 vectorize 788 -9.1%
Clang -O3 vectorize 1324 52.7%

Which goes on to show that the vectorizer is, indeed, working well for ARM, but the costs of using the VFP/NEON pipeline outweigh the benefits. Remember than NEON vectors are only 128-bits wide and VFP only 64-bit wide, and NEON has no double precision floating point operations, so they’ll only do one double precision floating point operations per cycle, so the theoretical maximum depends on the speed of the soft-fp libraries.

So, in the future, what we need to be working is the cost model, to make sure we don’t regress in performance, and try to get better algorithms when lowering vector code (both by making sure we match the patterns that the back-end is expecting, and by just finding better ways of vectorizing the same loops).


Without further benchmarks it’s hard to come to a final conclusion, but it’s looking good, that’s for sure. Since Linpack is part of the standard LLVM test-suite benchmarks, fixing this and running it regularly on ARM will at least avoid any further regressions… Now it’s time to get our hands dirty!


« Previous entries 

Creative Commons License
We Support



End Software Patents


See Also

The information in this weblog is provided “AS IS” with no warranties, and confers no rights.

This weblog does not represent the thoughts, intentions, plans or strategies of our employers. It is solely our opinion.

Feel free to challenge and disagree, and do not take any of it personally. It is not intended to harm or offend.

We will easily back down on our strong opinions by presentation of facts and proofs, not beliefs or myths. Be sensible.

Recent Posts