Well, I found out that if i run a cpu stress test (i am using mprime
'torture test') while running chrony, suddenly my PPS source std dev goes
stable below 300ns.
So i guess this is realted to some kind of cpu scheduling. However i
disabled the c-state options in the bios, my CPU frequency is not altered
according to /proc/cpuinfo, and yet i still have bad results unless i run
this stress test.
Any idea ?
2017-09-01 15:52 GMT+02:00 Miroslav Lichvar <mlich...@redhat.com>:
> On Thu, Aug 31, 2017 at 05:25:09PM +0200, Thibaut BEYLER wrote:
> > No I tested it on ordinary x64 kernel (4.9 , 3.16 etc..) coming from
> > & fc repos with no custom options.
> > I just installed pps-linux and invoked 'ldattach 18 /dev/ttyS0' (which
> > loads pps_ldisc module) , maybe i'm missing something ?
> I'm not sure. Maybe the hardware cannot do better. From what I have
> seen, with a real serial port (no USB, etc) the PPS is usually stable to
> 1 microsecond. For example, this is what I get with a Garmin 18x I have
> MS Name/IP address Stratum Poll Reach LastRx Last sample
> #* PPS0 0 4 377 8 +200ns[ +391ns] +/-
> Name/IP Address NP NR Span Frequency Freq Skew Offset Std
> PPS0 11 6 161 +0.001 0.015 +18ns
> Miroslav Lichvar
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