Higher CPU utilization from 27% to 65% between 6a04c45 and cce47b6 on RPi4B+

[xaelsouth]

Higher CPU utilization from 27% to 65% between 6a04c45 and cce47b6 on RPi4B+

[xaelsouth]

Hello Damian, many thanks to you - as a tormented Subversion user now I know what git bisect is and for what it is good. :-) To your question about performance: 1) the FIR filter for the T1/C1 mode is now a little bit longer resulting in slightly higher CPU utilization (older FIR filter was incorrectly designed regarding the stop band frequency - it's mentioned in the README). Here is nothing what I can do for better performance. 2) i have implemented S1 mode that effectively doubles the CPU utilization. Here I could add an option to switch S1 off and an another option to switch T1/C1 modes off. 3) the "run length method", which is running in parallel to the old time 2 method, is unfortunately not for free, but shows (at least for me) reduced CPU utilization. What _you_ could do here:     a) to switch the run length method off by adding "-r 0" to the command line     b) or to switch the time 2 method off by adding "-t 0" to the command line     c) or add "-a" to the command line for using inaccurate atan version - you should test that a little bit carefully.     d) you can freely combine a) and c) or b) and c).         I would definitely try with b) and c) first. If you have problems with receiving datagrams then try with b) only. Let me know if you was successful with that. Xael

[dwrobel]

Thank you for the comprehensive explanation.

ad. 3) Here is the result of my experiments:

3) option	rtl_wmbus option	CPU usage [%]	Comments
a)	-r 0	63	Rejected due to negligible CPU utilization drop
b)	-t 0	57	Unusable due to observed CRC errors
c)	-a	50	Works properly
b) and c)	-a -t 0	40	Unusable due to observed CRC errors

Based on above the only option which works is p. 3) option c) thanks to this the CPU utilization dropped from initial 65% to 50%.

If you think it might be valuable to test anything from other points 1) and 2), please let me know I'm open to your suggestion.

[xaelsouth]

Hello Damian,

thanks for testing. You could go well with the "-a" option if you don't observe any CRC errors or if CRC errors are rare enough.

Anyway, for rtl_wmbus I have implemented a new command line option: use "-p S" to turn S1 mode off (I guess you don't need S1 at all) or use "-p T" to turn T1/C1 mode off . CPU utilization should drop to a half of the original one after that.

[dwrobel]

Great, I'll give it a try.

[anonymous-one]

Was running a year+ old build of wmbusmeters and decided to roll the latest today and noticed my load jump after upgrading everything related... Luckily found this thread and back down we go.

Thanks guys!

[xaelsouth]

Seems not to be a issue as nobody complains anymore ;P