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

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Ray Lee wrote:
On 5/19/07, Bill Davidsen <[email protected]> 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.
Finally, if it is the standard deviation (of either), then I don't
really believe those numbers for the glxgears case. The deviation is
huge for all but one of those results.

I had the same feeling, but because of the code error above, what failed was zeroing the sum of the errors, so (a) values after the first kept getting larger, and when I debugged it against the calculation by hand, the first one matched so I thought I had it right.

Regardless, it's good that you're doing measurements, and keep it up :-).

Okay, here's a bonus, http://www.tmr.com/~davidsen/sched_smooth_02.html not only has the right values, the labels are changed, and I included more data points from the fc6 recent kernel and the 2.6.21.1 kernel with the mainline scheduler.

The nice thing about this test and the IPC test I posted recently is that they are reasonable stable on the same hardware, so even if someone argues about what they show, they show the same thing each time and can therefore be used to compare changes.

As I told a manger at the old Prodigy after coding up some log analysis with pretty graphs, "getting the data was the easy part, the hard part is figuring out what it means." If this data is useful in suggesting changes, then it has value. Otherwise it was a fun way to spend some time.

--
Bill Davidsen <[email protected]>
  "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot
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