Re: [RFC] new timeofday core subsystem (v.A1)

[Christoph Lameter]

On Tue, 7 Dec 2004, john stultz wrote:

> +/* __monotonic_clock():
> + *		private function, must hold system_time_lock lock when being
> + *		called. Returns the monotonically increasing number of
> + *		nanoseconds	since the system booted (adjusted by NTP scaling)
> + */
> +static nsec_t __monotonic_clock(void)
> +{
> +	nsec_t ret, ns_offset;
> +	cycle_t now, delta;
> +
> +	/* read timesource */
> +	now = read_timesource(timesource);
> +
> +	/* calculate the delta since the last clock_interrupt */
> +	delta = (now - offset_base) & timesource->mask;
> +
> +	/* convert to nanoseconds */
> +	ns_offset = cyc2ns(timesource, delta,0);
> +
> +	/* apply the NTP scaling */
> +	ns_offset = ntp_scale(ns_offset);

The call to ntp_scale will significantly impact clock retrieval
performance. ntp_scale needs to be removed. Could you simply let the clock
run with a scaling factor (just make sure the scaling factor is a bit
slower than ntp time and then skip a few nanoseconds of time forward
at the next correction?)
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