[ntp:questions] Which version of Linux works best?

Terje Mathisen "terje.mathisen at tmsw.no" at ntp.org
Fri Mar 12 09:25:36 UTC 2010

David Woolley wrote:
>> So? The interrupt still takes the same time to be activated. On a GHZ
>> system, there is enough time in 1usec to run 1000 commands, and it is
>> hard to imagine that many being used to return the ioctl. I have worried
> That's 1000 machine cycles, not 1000 instructions. On modern systems,
> I'm not sure that 1000 cycles isn't a typical time for a system call on
> modern, high level language progammed, bloatware. (I seem to remember
> hand coding an ISR in assembler to a budget of 100 instructions (for
> 68000) and it not being that easy.)

Interrupt times are quite often in the multi-K cycle count for modern 
operating systems. :-(

For ntp it is the variability that really counts, a constant response 
time will just lead to a small but fixed offset from the true time. If 
you really care you can fudge away that offset. :-)


- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"

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