RELENG_4 -> 5 -> 6: significant performance regression

[Kris Kennaway]

On Fri, May 12, 2006 at 11:25:58PM +0300, Dmitry Pryanishnikov wrote:
> 
> Hello!
> 
> On Fri, 28 Apr 2006, Kris Kennaway wrote:
> >>>>makeoptions	CONF_CFLAGS=-fno-builtin
> >I don't know, it needs to be tested in your particular case.
> 
>  I've built another kernel, adding back
> 
> makeoptions  CONF_CFLAGS=-fno-builtin
> options      QUOTA
> 
> Results are almost the same as w/o these 2 options. So the following 
> overhead difference:
> 
> >>>>                %Sys   %Intr   %Idl
> >>>>RELENG_6 + rl0      45      40     15
> >>>>RELENG_6 + fxp0     45      35     20
> >
> >>                  %Sys   %Intr   %Idl  "time md5 -t" wall clock time
> >>RELENG_6 + rl0      34      24     42   1:43
> >>RELENG_6 + fxp0     30      20     50   1:40
> 
> is caused by just these:
> 
> options 	INVARIANTS
> options 	INVARIANT_SUPPORT

So what is the overall status?  I am not clear what your results are.

>  As my transfer takes much time (say 10 minutes) I've observed % of time
> used many times during the transfer - they don't vary more than +/- several
> (2-3) % during the main transfer phase (when transfer speed is stable).
> My "time md5 -t" runs was used only as a confirmation that systat's numbers
> are trustworthy - they simply confirm that there are _much_ less CPU cycles
> available for application under RELENG_5/6 than under RELENG_4 (under 
> identical load pattern). I ran "time md5 -t" several (3-5 times) just to
> confirm my assumptions, and results didn't vary more than 3%. So I suppose
> that ministat isn't necessary in my tests.

Perhaps not when the difference is large, but you need to be very
careful when differences are below ~10%, because it's easy to make
incorrect conclusions.

Kris
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