gprs_rlcmac_received_lost() in gprs_rlcmac_meas.cpp

Daniel Willmann dwillmann at sysmocom.de
Mon Nov 18 15:56:23 UTC 2013


Hello Andreas,

while looking through the osmo-pcu code to figure out why some
connections stall we had some problems making sense of the elapsed time
calculations in gprs_rlcmac_meas.cpp.

Could you confirm/deny my assumptions about it or explain the idea
behind it?

> gettimeofday(&now_tv, NULL);
> elapsed = ((now_tv.tv_sec - loss_tv->tv_sec) << 7)
> 	+ ((now_tv.tv_usec - loss_tv->tv_usec) << 7) / 1000000;

I assume here you're calculating the duration of the measurement period
so far and since you want to have sub-second accuracy you multiply
everything with 128. Why 128?
Is it becasue it simplifies the throughput calculation?
(tbf->meas.dl_bw_octets/elapsed in gprs_rlcmac_dl_bw())

> if (elapsed < 128)
> 	return 0;

Is the intention here that the duration of the measurements is supposed
to be one second? So every second these measurements are printed out and
reset?


Regards
Daniel Willmann

-- 
- Daniel Willmann <dwillmann at sysmocom.de>       http://www.sysmocom.de/
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