Yo Hal! On Wed, 28 Sep 2016 11:14:49 -0700 Hal Murray <hmur...@megapathdsl.net> wrote:
> gemiller > I have a hard time believing a PLL > running at user timer interrupt time > can be anywhere as good as a kerenl > PLL running at TICK intervals. > > There are two parts to this discussion. There is the PPS time stamp > and the PLL. No. PPS is unrelated to the kernel PPL. It is a totally separate kernel module. > The PPS time stamp gives you the data to work with. Yes. > The work can be > done in user space or in the kernel. Yes, but not as well in user space. > New samples arrive every > second. No. Twice a second. But now you are confusing the PPS with the PLL. > Suppose I use the same algorithm. Running the code in user > space adds a few sub-ms kernel calls. And a LOT more jitter. > (I'm assuming the scheduler > cooperates.) Bad assumption. > I don't think that minor delay will be significant. Agreed, but the jitter is. Also the frequency of updates is different by orders of magnitude. > The kernel PLL is probably using different parameters than ntpd. As I have just seen. Very dufferent results. > gemiller > yes, best to measure > > Check your clockstats on your minpoll-0 runs and see if it really was > running at 0. Yes, it was. That is the recent bug fixes. > On my quick tries, it was actually running at 1 (2 > samples per batch) I didn't track it down. Until Sep 26, then it got fixed. But once again, unrelated to PPS or PLL. RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 g...@rellim.com Tel:+1 541 382 8588
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