Re: [PATCH] More time clean up stuff.

[george anzinger <george@mvista.com>]

Riley Williams wrote:
> Hi George.
> 
> I'm ignoring the rest of this - it makes sense to me, but I'm
> no expert in it. However, your last point is one I can comment
> about as I've dealt with it professionally many times.
> 
>  > clock_nanosleep is changed to round up to the next jiffie to
>  > cover starting between jiffies.
> 
> Isn't this a case of replacing one error with another, where
> one of the two errors is unavoidable?
> 
>  1. In the old case, the sleep will on average be half a jiffie
>     LESS than the requested period.
> 
>  2. In the new case, the sleep will on average be half a jiffie
>     MORE than the requested period.
> 
> One or the other is unavoidable if a jiffie is the basic unit
> of time resolution of the system. However, the error is totally
> meaningless if we are asking to sleep for more than 15 jiffies.

I had a hard time justifiying this also.  I would really like to have 
better resolution.  As to which choice to make, the standard is VERY 
clear here:  No timer or sleep shall complete BEFORE its time.
> 
> Best wishes from Riley.
> ---
>  * Nothing as pretty as a smile, nothing as ugly as a frown.
> 
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-- 
George Anzinger   george@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml