so, the unit of master offset is nanosecond?how to convert to ppb? 2015/8/30 上午2:10於 "Richard Cochran" <[email protected]>寫道：
> On Sat, Aug 29, 2015 at 06:09:56PM +0100, Guo Hao wrote: > > ptp4l[7726.711]: master offset -8 s2 freq +3835 path delay > > 825 > > > > Does this mean the clock offset between the 82574 NIC and the Master > Clock > > is in the range less than 100 ns? > > Yes. > > > Does that mean the system time is synchronized to the ptp hardware clock > on > > the 82574 NIC? > > Yes, but remember that there is probably some offset in the low > microseconds range. The "delay" tells you that reading the PHC time > over the PCIe bus takes about 13 microseconds. > > > However I cannot run ptp4l and phc2sys as a daemon process under Ubuntu: > > > > root@Hao-Ubuntu:~# service ptp4l start > > ptp4l: unrecognized service > > root@Hao-Ubuntu:~# > > > > Any idea on this? > > Just start the programs by hand. To start them automatically, one > easy way is to put the commands into /etc/rc.local. > > > Therefore, I doubt whether there is a inherent delay between the point > when > > the Ethernet capture card request for the ToD and point the Ethernet > > capture card really gets the information or the system time is not > > synchronized by the hardware clock of the 82574 NIC. > > But you said, > > the Ethernet capture card gets the 1-PPS from the same GPS clock. > > so the ToD from the host is irrelevant. The capture has the GPS's > 1-PPS, and so the phase of its time stamps should be correct to a few > hundred nanoseconds. > > The ~1 usec difference is probably just the sum of the GPS device's > egress latency and the capture card's ingress latency. The number is > perfectly reasonable, if one or both of the devices has MAC time > stamping. > > HTH, > Richard > > > > ------------------------------------------------------------------------------ > _______________________________________________ > Linuxptp-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/linuxptp-users >
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