keeping simple

Category: systems

  • Adding value to Windows

    Andy Bechtolscheim says: It’s really hard to add value to Windows. Whatever you add, Microsoft is going to take away from you. Linux has opportunities. There are many ways to add value. There are lots of things Sun customers expect that are missing from Linux The first two sentences are relatively common wisdom. The last…

  • Plagiarism watch

    Thanks to google code watch I see that an open source real-time Linux project has reached new heights of originality – changing the magic number that they copied from RTLinux 10 years ago to a new number. The constant definition #define RT_TASK_MAGIC 0x754d2774 which was in very early versions of RTLinux and appeared every previous…

  • The Embedded Enterprise, Pruit-Igoe, Ayn-Rand, the telecommunications stack and why software does not suck

    Programmers will readily tell you that “Windows sucks” or “Linux sucks” or “POSIX sucks” why this or that software is badly designed, bloated, slow, buggy, un-needed, ugly, and generally disgusting. But, Windows is actually an immensely useful and sophisticated program with astounding capabilities – Linux is too. POSIX is a comprehensive solution to many difficult…

  • Back from India

    We were going into a government facility in Mumbai, and the guard points at me and asks, as if finding it hard to believe “He is a foreigner?” This was my fourth visit to India and, like all the others so far, mostly a rushed series of meetings and trips to airports, but I got…

  • Soft real time continues to sag

    Paul McKenney once wrote: Despite such complications, priority inheritance works reasonably well for exclusive locks, and is a major component of Ingo Molnar’s CONFIG_PREEMPT_RT patch. There are strongly held opinions both for and against priority inheritance, for example. http://www.linuxdevices.com/articles/AT7168794919.html in which Victor Yodaiken considers priority inheritance to be harmful, and, as near as I can…

  • Soft real-time and soft design strategies versus QOS

    [ see revised version ] (edited August 18 2007 to add back link and formatting) “Soft real-time” is a perfect example of the “soft design” I was complaining about in the previous post. There are perfectly good ways of characterizing quality of service assurances. For example, you could say that the average = x and…

  • Programming design style

    Someone needs to come up with a slick name for “designed to fail during test instead of production” or for the more common “soft” type of programming. When we write code, we assume we screwed up somewhere, an assumption based on years of bitter experience (well, we assume someone screwed up, maybe in the tools,…

  • The embedded enterprise

    It is now possible to put together sophisticated and powerful embedded and control systems that are mostly composed of pre-existing working software. One of the demonstrations we showed at AMD’s recent embedded workshop was a small two processor (4 core) box running RTLinux and Windows XP. Embedded development teams for RTCore based products can mirror…

  • Speculation on modularity and information theory

    One way of defining modules is by what engineers have to know. If a program X consists of components X1 … Xn then we can say Xi is a module if a programmer can modify it without learning “much” about any other module. A second, related measure can be in terms of information hiding –…

  • multicore and virtualization and real-time provisioning

    We added the “reservation” capability to RTCore real-time POSIX threads a couple of years ago. Normally, the client platform operating system shares the processor with RTCore threads as a completely pre-emptible low priority thread. This works exceptionally well. Worst case interrupt latencies of under 10 microseconds on Opterons and under 20 on Arm9s are possible…