Kernel PLL (from IRC)

[Hal Murray]

gemiller:
  Being the whole point of ntpd, to
  manage the kernel PLL, this should be
  obvious.

No.  The purpose of ntp is to maintain the correct system time.

ntpd itself is a PLL.

The purpose of the Kernel PLL is to do the same things with
PPS pulses but do it better.  It may have been important back
in the old days when systems were slow and schedulers were crappy.

I don't know how important the Kernel PLL is today.  It's not in most distros
so it's obviously far from critical.  The only way to test is to build a
kernel and collect data, then compare that with what we can get without it.


esr
  The other is that it kills the
  TESTFRAME concept, or at least
   damages its usefulness pretty badly.
   Logs from PLL systems won't be  ...

I don't see the problem.  TESTRAME is testing ntpd, not the kernel.  It
records everything that goes in/out of ntpd.  Replay should do the
same even if run on a different sysem/OS/architecture.

(There might be some differences between 32/64 bit systems.)




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