[time-nuts] Linux time servers

Hal Murray hmurray at megapathdsl.net
Thu May 14 22:00:29 UTC 2009


> Is there any consensus for the reasons why Linux performs poorly?  I
> was thinking about setting up a server as well (possibly using a
> little ARM-based single-board computer that runs Linux). 

Consensus?  I doubt it.

My reading.  Lots of cooks.  None of them are time geeks.

There are a lot of people working on Linux.  A lot of them are smart.  A lot 
of them are not plugged into the culture of key chunks of technology so they 
"fix" or "clean up" some code in ways that actually breaks things.

There are "only" a few big screwups that are on my list these days.
  No PPS support.
  The TSC calibration code is broken.  (and it's the default mode)
  The in-kernel NTP support code is broken.

The last two work, just not quite correctly.  They are close enough so that 
you probably won't notice any problems unless you are a geek.

One of the things that is driving some of the changes is making things work 
better for low power applications.  The old scheduler used to do a bit of 
work every clock tick (100 HZ to 1000 HZ).  That chews up a lot of power if 
your battery powered system goes to sleep when there is nothing to do.  So it 
seems reasonable to look ahead in the scheduler queue and figure out how long 
until the next time there is work to do and sleep until then.
 



-- 
These are my opinions, not necessarily my employer's.  I hate spam.






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