Saturday, June 13, 2009

Reading notes of internals of the RT patch

  1. Real-time is something about predictability instead of performance, throughput or latency. That is, real-time system may have worse average throughput or latency, but it will have better largest latency or lowest throughput. Linux kernel have great average performance but the worst one is not so good.
  2. The drawback of Robert Love's kernel preemption patch is: A high priority process must still wait on a lower priority process while it is in a critical section, even if that same high priority process did not need to access that section.
  3. The RT patch is all about determinism and being able to have full control of the kernel. But, like being root, the more power you give the user the more likely they will destroy themselves with it. Such as, a user process can have higher priority than IRQ handler, if the process holding the CPU, system will hang.

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