[ntp:questions] Power-saving patch to NTP

Uwe Klein uwe_klein_habertwedt at t-online.de
Sun May 18 15:14:11 UTC 2008


David Woolley wrote:
> Uwe Klein wrote:
> 
>> Danny Mayer wrote:
>>
>>> It's not doing nothing. If the CPU is on standby nothing, including 
>>> ntpd, should be running.
>>
>>
>> ntp would then need to accomodate thinks like a "sleep mode"?
>> and a "trigger" of type "Query the associations now"
>> ( on linux forex be d-bus aware? )
> 
> 
> The impression I get is that ntpd should be treated as infrastructure, 
> and have power management states, but Red Hat are treating it as an 
> errant application that needs to be modified to avoid upsetting the 
> power management apple cart.

Hello David,
I am not surprised.

Linux presents afaik the biggest userbase for ntp (and is simultanously
the most derided group of questioneers in this NG, though i think compared
to the installed instances linux is imho underrepresented).
If a large group is beat over the head in a somewhat regular fashion
( which may have been just a cats and dogs thing ) it is rather
unsurprising to find those people working around this obstacle.


  E.g. after resume from RAM, it needs to
> progress the clock discipline algorithm forwards (including extra 
> corrections for temperature excursions) before anything is allowed to 
> read the value of the clock, and after resume from disk, it should 
> probably do a restart.
Well it should start with ntp getting signaled to prepare for various
modes of sleep or cpu frequency slowdown.
Save as much state as is possible, then ack for sleep.

There is actually another situation where currently ntp is just
killed of and started again: network interface changes.
This could be handled in a less disruptive way as well.
> 
> The latter greatly increases the importance of fast convergence, and 
> without specific compensation for temperature variation, even resume 
> from RAM needs the ability to respond fast to frequency hits, possibly 
> conditioned on just having done a resume.
Whichever way one does this ntp needs to be able to respond to finer
grained external triggers. It can not any longer be "King of the Castle".

G!
uwe




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