Messages in this thread | | | Date | Thu, 2 Sep 2004 15:47:07 -0700 (PDT) | From | Christoph Lameter <> | Subject | Re: [RFC] New Time of day proposal (updated 9/2/04) |
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On Thu, 2 Sep 2004, john stultz wrote:
> On Thu, 2004-09-02 at 15:09, Christoph Lameter wrote: > > > timeofday_hook() > > > now = read(); /* read the timesource */ > > > ns = cyc2ns(now - offset_base); /* calc nsecs since last call */ > > > ntp_ns = ntp_scale(ns); /* apply ntp scaling */ > > > system_time += ntp_ns; /* add scaled value to system_time */ > > > ntp_advance(ns); /* advance ntp state machine by ns */ > > > offset_base = now; /* set new offset_base */ > > > > This would only work if the precision of the timer used is > > <=1ns and if you are actually able to caculate the nanoseconds that have > > passed. What do you do if the interval is lets say 100ns and the time the > > timeofday hook is being called can be anytime within this 100ns interval > > since the time source is not always precise? > > Well, with the exception of the TSC, none of the current time sources > have <=1ns resolution, but I'm not sure I understand the problem you're > trying to point out. Could you clarify? > > > I think its unavoidable to do some correction like provided by the time > > interpolator if the clock source does not provide ns. > > Could you point to the specific correction you describe?
I drop my objections. I was thinking too much in terms of the old code.... This should work fine. - 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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