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On 8 Dec 2004 at 11:58, john stultz wrote: [...] > behavior of adjtimex(). We need to be able to implement the following > adjustments within a single tick: > > 1. Adjust the frequency by 500ppm for 10usecs What do you mean by "for 10usecs"? > 2. After that adjust the frequency by 30ppm for the rest of the tick. I'm not sure what you are taling about: plain old adjtime() or the NTP kernel interface? [...] > I may have asked this before, but w/ 32 bit mult and shifts, how > granular can these adjustments be? Independent of any bits, the precision should be up to 1ns for reading and setting the clock, and as a consequence you might provide internal fractional nanoseconds (if you want to have a truly stable nanosecond clock model). If we get this right, there will be peace in this area until the wires in a PC are significantly shorter than 30cm (I think this is how far the light goes in 1ns). ;-) > > Also additional complications arise when we have multiple things (like > cpufreq) playing with the timesource frequency values as well. I see a bug difference between precise time keeping and "playing" with timesources. Regards, Ulrich - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
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