Steven Seeger wrote:
I compiled the kernel for 586 and am running the PIT timer. I still get the 17000-18000 context switches per second, and now the irq0 handler is taking up 11% of the CPU instead of only 5% when the two 8000Hz tasks are loaded but delayed on events. I think that the problem isn't withpit, but with the tasks being periodic even though they are blocked.
That makes sense: Periodic timers keep on firing. That would explain up to 16000 IRQ invocations per second. And the other 1000-2000 come from Linux?
As suggested earlier: you can reduce the number of IRQ events by basing your periodic tasks on the same start date. Then both will be woken up at the same times and their priority will decide about the execution order.
Running in PIT mode with periodic timing on uses only 9.5% of the CPU. I show about 9000 context switches per second. (the 2 8000 hz tasks and the 1000 hz linux interrupt.)
Do you need Linux at 1 KHz? You may even want to try NO_HZ.
With periodic timing, it's 5.4% when the tasks idle and about 9000 context switches a second. When one of them becomes active, the irq0 handler is using 10% of the CPU and the sound task is using about 8%. These are two kernel tasks.Userspace stack size is set to 64k. I forgot to mention this to Philippe earlier.Perhaps the problem is the overhead that the timer handler introduces being able to support multiple skins with individual timebases. It sounds like in order to save some cpu cycles, I may want to turn off periodicity while threads are idle and also avoid setting threadsperiodic when they can be driven some other way.
I'm still wondering with what older numbers you compare all the nice stats you now generate. Neither older Xenomai nor RTAI provide comparable statistics. Are we doing fair comparisons here?
Jan
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