keeping simple

Category: systems

  • OpenBSD developer notes king’s clothing is “virtual”

    Theo de Raadt explains why virtualization does not improve security. How about this: to improve security, you have to have a secure design, a marketing buzzword won’t do the trick. Anyone who has seriously looked that the current generation x86 virtualization hardware knows that it does not provide clean separation or levels of security. It…

  • Distributed shared memory from first principles

    [Update 10/16] What is the fundamental performance limiting factor that has dominated that last 30 years of computer architecture? The obvious answer is the disparity between processor and memory/storage speed. We connect processors to cache, to more cache, to even more cache, to some bus, to memory, to disk/network, suffering costs at each step as…

  • more on missed wakeup

    Here are some conventions [Update: typos fix, Friday] We are concerned with state machines and sequences of events. The prefixes of a sequence include the empty sequence “null” and the sequence itself. Relative state: If “w” is the sequence of events that have driven a system of state machines from their initial to their current…

  • The lost wakeup problem

    One basic problem in operating system design is how to make efficient blocking requests. Thread A wants something from Thread B (or ISR B) and (1) requests and (2) blocks. There are thousands of ways in which the interval between (1) and (2) can lead to a “missed wakeup”. That is, A requests, B signals…

  • OSIM Madrid and Value Manifolds

    Spent a couple of very interesting days at the OSIM conference in Madrid as part of my consulting for WindRiver which has a very powerful market position in cellular handsets now – partly due to their acquisition of RTLinux for embedded last January. Interesting to see these companies negotiate the vast complexity of the technology…

  • Apple’s strategic brilliance

    I may be reading too much into it, but Apple looks to have come up with a strategy to pass Microsoft in the next ten years. They are linking their phone, music, and PC business together to form an unavoidable platform in a way that has not been done since Microsoft put together the office…

  • Carbon neutral processors and ecocidal operating systems

    Carbon neutral processors and ecocidal operating systems

    Data centers are reckless consumers of power. Since modern processors leak somewhere in the neighborhood of 40% of their peak power consumption even when idle and since most measurements show that most computers are nearly always idle, that’s a lot of power wastage. RMI has some innovative thinking about data center design. The designers of…

  • Underlying requirement for hard real-time

    Simple point that is widely ignored: you need hard real-time capability to offer any meaningful “soft” real-time. Let’s suppose you say that you can drop up to N frames a minute or K< N frames over any 10 second period from a nominal H>N frames per minute feed. This is a typical soft real-time task…

  • universal machinery

    If even 20% of what Peter Gutman says is so, then I’ve been optimistic in my assessement of DRM.

  • Notes on unintended security effects

    I’ve been complaining about the security implications of DRM and “trusted computing” and “safe boot” for some time now. Susan Landau points out that the expansion of wiretapping has the same effect. Such threats are not theoretical. For almost a year beginning in April 2004, more than 100 phones belonging to members of the Greek…