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SCHED_FIFO and realtime throttlingSCHED_FIFO and realtime throttlingPosted Sep 4, 2008 11:24 UTC (Thu) by mb (subscriber, #50428)In reply to: SCHED_FIFO and realtime throttling by walken Parent article: SCHED_FIFO and realtime throttling
Yeah well, a hard (old style) RT process will also be interrupted once in a while by hardware interrupts. Sure, the time running an IRQ is a lot lower than the time a process is scheduled away, but still.
If you really care about not getting interrupted at all, you should be running inside of the kernel or probably with rtai or rtlinux.
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SCHED_FIFO and realtime throttling Posted Sep 5, 2008 10:27 UTC (Fri) by dmarkh (guest, #40670) [Link]
The thing is anyone actually having a dedicated machine to run that (old style) RT process is almost surely running on an SMP machine and has isolated his CPU from hardware interrupts and other processes. But even doing that, the kernel thinks that IT owns the CPUs in your box, not you, and requires some time on YOUR cpu regardless of your requirements. Folks, the kernel is just plain broken when you have 4 processors and cannot dedicate %100 of a single processor for a RT application. When you run a process at %100 on a single processor it breaks the kernel because the kernel can't get the processor for it's workque and other crap it thinks it needs to run on YOUR cpu. I think all this throttling crap is more of a "Lets not let userland break our kernel" sort of thing rather than "Lets not let user land break them selves" sort of thing.
I will admit though, for a non SMP box this is probably a good thing as a default setting.
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