Hi Luis, On 29 March 2018 14:54, Luis Claudio R. Goncalves wrote: > On Thu, Mar 29, 2018 at 07:30:27AM +0000, Phil Edworthy wrote: > > Hi John, Clark, > > > > On 28 March 2018 16:32, Clark Williams wrote: > > > On Wed, 28 Mar 2018 16:56:27 +0200 > > > John Ogness <john.ogness@xxxxxxxxxxxxx> wrote: > > > > > > > On 2018-03-28, Phil Edworthy <phil.edworthy@xxxxxxxxxxx> wrote: > > > > >> > I found that cyclictest results vary from one run to another. [...] > > I did some overnight tests with 100 runs of cyclictest running for 1 minute. > > Stats below were calculated using stats package from > > http://web.cs.wpi.edu/~claypool/misc/stats/stats.html > > > > 1. Interval fixed to 400us, not using --secalign > > Min: 20 Avg: 37 Max: 187 (avg of 100xMax is 134) > > > > 2. Interval fixed to 400us, using --secalign > > Min: 20 Avg: 37 Max: 177 (avg of 100xMax is 150) > > > > 3. Interval increases from 400 to 499, not using --secalign > > Min: 20 Avg: 37 Max: 211 (avg of 100xMax is 157) > > > > 4. Interval increases from 400 to 499, using --secalign > > Min: 20 Avg: 37 Max: 202 (avg of 100xMax is 157) > > > > While --secalign may provide more consistent results, it appears that > > it is not as good at identifying the worst case latency. > > It appears that testing different intervals is much better at > > identifying the worst case latency. > > Have you used the hwlat ftrace tracer or hwlatdetector.py from rt-tests in > order to verify if your system have SMI-induced latency spikes? That may not > be part of the problem described here, but spurious SMI spikes could > account to some of the discrepancies. This is on ARM, so no SMI. There's no BIOS, nothing like that. Thanks Phil -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
