> From: Akira Yokosawa <akiyks@xxxxxxxxx> > Sent: Friday, March 10, 2023 8:12 AM > To: paulmck@xxxxxxxxxx; Zhuo, Qiuxu <qiuxu.zhuo@xxxxxxxxx> > Cc: frederic@xxxxxxxxxx; jiangshanlai@xxxxxxxxx; joel@xxxxxxxxxxxxxxxxx; > linux-doc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > rcu@xxxxxxxxxxxxxxx; urezki@xxxxxxxxx; Akira Yokosawa > <akiyks@xxxxxxxxx> > Subject: Re: [PATCH v3] rcu: Add a minimum time for marking boot as > completed > > Hi, > > Let me chime in this interesting thread. > > On Thu, 9 Mar 2023 13:53:39 -0800, Paul E. McKenney wrote: > > On Thu, Mar 09, 2023 at 03:17:09PM +0000, Zhuo, Qiuxu wrote: > >> > From: Paul E. McKenney <paulmck@xxxxxxxxxx> [...] > >> > > > >> > > a's standard deviation is ~0.4. > >> > > b's standard deviation is ~0.5. > >> > > > >> > > a's average 9.0 is at the upbound of the standard deviation of b's [8.0, > 9]. > >> > > So, the measurements should be statistically significant to some > degree. > >> > > >> > That single standard deviation means that you have 68% confidence > >> > that the difference is real. This is not far above the 50% leval of random > noise. > >> > 95% is the lowest level that is normally considered to be > >> > statistically significant. > >> > >> 95% means there is no overlap between two standard deviations of a > >> and two standard deviations of b. > >> > >> This relies on either much less noise during testing or a big enough > >> difference between a and b. > > Appended is a histogram comparing 2 data sets. > > As you see, the one with v2 patch is far from normal distribution. > I think there is at least two peaks. > The one at the right around 9.7 seems not affected by the patch. > In such a case, average and standard deviation of all the data don't tell much. > > It is hard to say anything for sure with such small set of samples. > And the shape of the plot is likely to be highly dependent on machine setups. > > Hope this helps. Thank you Yokosawa for sharing the histogram to provide an intuitive view of these data points and your analysis. ;-) -Qiuxu
