How the KERNEL_PLL switch kills TESTFRAME

Gary E. Miller gem at
Wed Sep 28 22:15:51 UTC 2016

Yo Hal!

On Wed, 28 Sep 2016 15:09:46 -0700
Hal Murray <hmurray at> wrote:

> Part of the problem is that we have a word tangle between my use of
> "kernel PLL" and your use of "KERNEL_PLL".  I was referring to the
> PLL option in the Linux kernel that gets included when you say:

We never use that PLL.  No one should use that PLL with linux.  

So non-sequiter.

> I have access to Linux, NetBSD, and FreeBSD.  ntpd runs on all 3 and
> does essentially the same thing.  The key ideas are being able to
> adjust the clock "drift" and being able to slew the clock.

Which in the end are the same things.

> You said "adjtimex".  There is also ntp_adjtime.  It's available on
> Linux, NetBSD, and FreeBSD.  It's covered in RFC 1589.

So why do we use adjtimx()?

> How well does it work if you build to use ntp_adjtime?  Does that do 
> something silly like kill using the kernel PPS time stamping?

From: man 2 adjtimx

"the constants used for ntp_adjtime() are equivalent but differently

   ntp_adjtime ()
       The ntp_adjtime() library function (described in the NTP "Kernel
       Appli‐ cation Program API", KAPI) is a more portable interface
       for performing the same task as adjtimex().  Other than the
       following points, it is identical to adjtime():

       * The constants used in modes are prefixed with "MOD_" rather
         than "ADJ_", and have the same suffixes (thus, MOD_OFFSET,
         MOD_FREQUENCY, and so on), other than the exceptions noted in the
         following points.

       *  MOD_CLKA is the synonym for ADJ_OFFSET_SINGLESHOT.

       *  MOD_CLKB is the synonym for ADJ_TICK.

       * The is no synonym for ADJ_OFFSET_SS_READ, which is not
         described in the KAPI.

Seems interchangeable to me.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at  Tel:+1 541 382 8588
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