Hello Richard, On 18 Feb 2014, at 16:57, Richard Cochran <richardcoch...@gmail.com> wrote:
> On Wed, Feb 12, 2014 at 09:58:07PM +0100, dbrign...@audioscience.com wrote: >> From: Delio Brignoli <dbrign...@audioscience.com> >> >> Peer delay should never be negative, when it occurs >> warn the user and drop it. > > I don't think it is right to drop such measurements. If the clocks are > far enough apart in frequency and the response turn around time long > enough, then the value can be negative. Although a negative delay is > intuitively wrong, still the value reflects the true frequency offset > between the peers, and using the value will help to syntonize the > slave to the master. > > Even in the gPTP case where you do not tune the clock, still I would > expect that you need the actual peer delay measurement (even when > negative) in order to calculate the true offset from master. I had seen the changes related to path delay but, when preparing this patch, I conflated the P2P case with gPTP one so I thought I would not be affecting anything else but the gPTP case; my bad. I also assumed the peer delay had to be non-negative to be meaningful. Would you be OK with a patch that introduced a minimum acceptable peer delay configuration option? Thanks — Delio > [ Originally I had the same check on the path delay, but I later > decided that not including the negative measurements can hurt the > servo or even prevent its operation altogether. I did leave a > warning message, but since this occurs so often in practice, the > messages became annoying and were downgraded in debug messages. See > clock_path_delay() in clock.c. ] > > Thanks, > Richard ------------------------------------------------------------------------------ Managing the Performance of Cloud-Based Applications Take advantage of what the Cloud has to offer - Avoid Common Pitfalls. Read the Whitepaper. http://pubads.g.doubleclick.net/gampad/clk?id=121054471&iu=/4140/ostg.clktrk _______________________________________________ Linuxptp-devel mailing list Linuxptp-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
