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Embedded Linux Conference 2010
So, today was the last day of the Embedded Linux Conference. Now, I’ll be here in USA for the Linux Collaboration Summit. It was really cool and it was amazing to meet people you are only used to chat, exchange some emails or that you heard about. Just to name some: Steven Rostedt, Greg Kroah-Hartman, Frank Rowand, Mike Anderson, Andrew Morton, Jon Corbet and others. I was really impressed too seeing Rostedt programming or Greg answering emails. What a great guys
And yesterday I presented my work, talking about the optimization of the Linux scheduler for soft real-time when running on multi-core architectures. I must admit I was a bit nervous, but it seems that people liked it. Following some pictures:
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Banco do Brasil + Linux 64 bits
Faz 1 mês mais ou menos que liguei no Banco do Brasil reclamando que a “solução de segurança” do site deles não estava funcionando no meu Linux 64 bits. Sem grandes surpresas, depois de me perguntarem se eu tinha a VM java da sun instalada, versão, etc, eles me passaram para o suporte de segundo nível. Pediram o meu telefone, dizendo que entrariam em contato (isso foi no sábado).
Logo na segunda-feira de manhã me ligaram e após mais um tempo conversando, ele disse: “o problema é que a nossa solução de segurança não é homologada para a jre 1.6. Acontece que em algumas plataformas ela funciona, mas não é garantido. A gente sabe que em Linux 32 bits funciona, mas a jre 1.5 é que é oficialmente homologada”. Então eu tinha duas opções: ou instalar a versão 1.5 ou rodar um browser 32 bits. Felizmente no meu sistema, archlinux, já tem um pacote firefox32 que faz tudo o que preciso e foi o a solução que adotei. Até hoje.
Hoje quando fiz meu usual “sudo pacman -Syu” para instalar atualizações de todos os pacotes, vi que tinha uma atualização da jre para ser feita: jre-6u18-2. Aí pensei… quem sabe nessa versão mudou alguma coisa que fez funcionar o applet do BB? Sem muitas esperanças, abri o site no chromium e para minha surpresa, funcionou! Abri no Firefox, e funcionou também. Pra tirar a dúvida, fiz o downgrade para a versão anterior do java, jre-6u17-1. Abri novamente e continuou funcionando. Logo, não foi causada pela atualização da VM, mas sim por alguma mudança que o pessoal do Banco do Brasil fez. Não sei se eles chegaram a homologar a versão 1.6 da JVM (o que já estaria mais do que na hora), só sei que agora funciona com Linux 64 bits.
Felizmente agora posso acessar a minha conta no Banco do Brasil sem precisar do browser 32 bits. Já estou removendo-o. Deixe seu comentário pra eu saber se funcionou pra você também (inclusive aqueles que usam FreeBSDs e outros unixes).
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Amazing kernel related blog
Today while reading “posts” on Buzz and digging in my RSS reader, I found this blog: http://smackerelofopinion.blogspot.com/ made by an ubuntu engineer. How many amazing posts there are on this blog. Particularly interesting is the one about ACPI Debugging and the other about perf, the tool I posted about some days ago (although it covers just a tiny amount of things this tool is capable of).
When I have some spare time I’ll try to use that first post to debug the ACPI on my buggy asus laptop, where temperature goes sometimes as high as 90 °C. Last year I tried to adjust the hysteresis curve of the fan control in order to have a cooler laptop but had no success on it.
PS.: I wished a day had 48h to be able to read all the cool stuff out there
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Chromium
After reading this post at “Linux Today” I decided to install the so expected Linux version of Chrome, the Google’s browser.
As I use Arch Linux, I haven’t expected to have a compiled version linked directly by the chromium’s website. Instead, I was hoping Arch’s developers already packaged it. And, with no big surprises, they did. Just to clarify a thing before continuing: Chromium is the open source projected behind Chrome (which is not opensource).
I’m not writing this post to repeat what’s already written there. So read it too. As opposed to his impression however, I’m running it without big problems: pages are rendered well formatted, without html or css problems. Sure, it’s not a browser to use everyday yet, but as a pre-alpha version it’s doing pretty good. Below, a picture with this post been written.
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Playing with your cache
Another possible titles could be “how to really slow down your computer” or “why caches are so important in computer architectures”. I started playing with turning my cache on and off last week using Linux because there are some situations in which you have to know why a piece of software is not working as expected. A possible problem could be the well known cache trashing, in which the contents of the cache is thrown away very often. Turning it down may give an answer if this is really the problem since now even running very slowly this variable is eliminated.
For example in my stage we had some tests showing that in certain scenarios a quad-core machine is much slower than an equivalent single or dual core. Next post I’ll show how to play with your cores, activating and deactivating them, so you may create your own programs and test them against a 1, 2, 3,… cores machine.
Also I think it’s a good exercise to students of computer science/engineering who are enrolled in courses as “computer architectures” and “operating systems”. For those, two good books: “Modern Operating Systems” by Tanenbaum and “Computer Architecture: A Quantitative Approach” by Hennessy and Patterson.