Hi, On 29 March 2018 08:30, Phil Edworthy wrote: > On 28 March 2018 16:32, Clark Williams wrote: > > On Wed, 28 Mar 2018 16:56:27 +0200 John Ogness wrote: > > > On 2018-03-28, Phil Edworthy wrote: > > > >> > I found that cyclictest results vary from one run to another. > > > >> > > > > >> > [...] > > > >> > > > > >> > Is it common knowledge that cyclictest results vary so much > > > >> > from one run to another? Any ideas how to mitigate this? [snip] > > > > cyclictest -m -n -Sp99 -i200 -h300 -M -D 10h [snip] > Ok, I have changed the pri to 98, no difference in the results that I can see. > > 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) > > 3. Interval increases from 400 to 499, not using --secalign > Min: 20 Avg: 37 Max: 211 (avg of 100xMax is 157) I've got a bit further with this. The max latency seen by cyclictest depends on the type of network load used during the test (duh!). I use a host PC to ping flood the board under test, however on my board (a low-end ARM board), the *size* of the ping affects the measured latencies. Using a ping size of 65506, cyclictest reports significantly higher average and max latency than if I use the default ping size of 56 bytes. In addition to the ping size affecting the results, the cyclictest interval also affects the latency seen. By running cyclictest for short durations with the interval sweeping from 400us to 500us, I get significantly higher max latency than just using an interval of 400us for many hours. So, is ping flood a good networking load for cyclictest? Any suggestions for non-network related loads that can be used whilst running cyclictest? Then I can determine if it is the GMAC hardware/driver. Any help appreciated! 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
