Markus Franke wrote: > Dear all, > > I am running some latency tests with irqbench/irqloop. I am wondering > whether it would be possible to achieve better results when activating > CONFIG_PREEMPT and CONFIG_PREEMPT_VOLUNTARILY during the kernel > configuration and running irqloop in User Mode over this kernel?
Nope. > Does it make any sense? Nope. :) > I think in theory it should give better results because > this irqloop runs in secondary(linux) domain when started, right? An > increasing preemptibility of the linux kernel should be better for the > irqloop-task. The Linux kernel is already fully preemptible by Xenomai once you applied the I-pipe patch. Therefore, you are free to pick the Linux preemption strategy according to your *Linux* load, independent of what the real-time part needs. Unless you have interactive Linux programs running, I can suggest to pick PREEMPT_VOLUNTARILY or even PREEMPT_NONE, specifically on low-end hardware. > All tests were made under heavy I/O and CPU load by means of "dd", > "pingflood" and "cpuburn". Nevertheless, I can only achieve worse > results when activating CONFIG_PREEMPT. Do you have CONFIG_DEBUG_PREEMPT set as well then? This option still as a small but measurable impact on Xenomai due to micro-dependencies that as scheduled to be removed in the near future. Jan
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