Re: Sched - graphic smoothness under load - cfs-v13 sd-0.48

[Matt Keenan]

Bill Davidsen wrote:
> Ray Lee wrote:
> > On 5/19/07, Bill Davidsen <davidsen@xxxxxxx> wrote:
> > > I generated a table of results from the latest glitch1 script, using an
> > > HTML postprocessor I not *quite* ready to foist on the word. In any 
> > > case
> > > it has some numbers for frames per second, fairness of the processor
> > > time allocated to the compute bound processes which generate a lot of
> > > other screen activity for X, and my subjective comments on how 
> > > smooth it
> > > looked and felt.
> > >
> > > The chart is at http://www.tmr.com/~davidsen/sched_smooth_01.html for
> > > your viewing pleasure.
> >
> > Is the S.D. columns (immediately after the average) standard
> > deviation? If so, you may want to rename those 'stdev', as it's a
> > little confusing to have S.D. stand for that and Staircase Deadline.
> > Further, which standard deviation is it? (The standard deviation of
> > the values (stdev), or the standard deviation of the mean (sdom)?)
> What's intended is the stddev from the average, and perl bit me on 
> that one. If you spell a variable wrong the same way more than once it 
> doesn't flag it as a possible spelling error.
>
> Note on the math, even when coded as intended, the divide of the 
> squares of the errors is by N-1 not N. I found it both ways in online 
> doc, but I learned it decades ago as "N-1" so I used that.
N-1 is for estimating the standard deviation from a random sample of a 
population (s), N is for calculating the standard deviation of a whole 
population (Ï).

xref http://en.wikipedia.org/wiki/Standard_deviation

Yes, I am aware of the potential for Wikipedia articles to be wrong, but 
this article seems correct at first blush :)

Matt


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