Markus Franke wrote: >> Hmm, I should have better said "tiny". This experience is based on >> I-pipe tracer observations, and I guess you don't have that thing on, >> have you? > > I have set: > > ---snip--- > # CONFIG_IPIPE_DEBUG is not set > CONFIG_IPIPE_TRACE_ENABLE_VALUE=0 > ---snap--- > > in both kernels (either with preempt or without). > >> How much is the difference? How long did you measure to exclude noise. > > The difference is about 1 us (in average and worst case) when running > irqloop in IRQ handler mode. > > I have been running the measurements for 1 minute under heavy load with > an interrupt frequency of 1 ms. This gives 60000 samples. Is this too > less in order to exclude noise?
1 us is definitely in the noise region even on today's high-end PCs, specifically when running the test that short. 1/2 hour, or better several hours are required to gain reliable worst-case numbers. Regarding the average, your test duration is likely enough. It indicates that CONFIG_PREEMPT worsens the cache hit-rate slightly. Jan
signature.asc
Description: OpenPGP digital signature
_______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help
