Re: [REPORT] cfs-v5 vs sd-0.46

[Ingo Molnar <mingo@elte.hu>]

* Michael Gerdau <mgd@technosis.de> wrote:

> > Here i'm assuming that the vmstats are directly comparable: that 
> > your number-crunchers behave the same during the full runtime - is 
> > that correct?
> 
> Yes, basically it does (disregarding small fluctuations)

ok, good.

> I'll see whether I can produce some type of absolute performance 
> measure as well. Thinking about it I guess this should be fairly 
> simple to implement.

oh, you are writing the number-cruncher? In general the 'best' 
performance metrics for scheduler validation are the ones where you have 
immediate feedback: i.e. some ops/sec (or ops per minute) value in some 
readily accessible place, or some "milliseconds-per-100,000 ops" type of 
metric - whichever lends itself better to the workload at hand. If you 
measure time then the best is to use long long and nanoseconds and the 
monotonic clocksource:

 unsigned long long rdclock(void)
 {
	struct timespec ts;

	clock_gettime(CLOCK_MONOTONIC, &ts);

        return ts.tv_sec * 1000000000ULL + ts.tv_nsec;
 }

(link to librt via -lrt to pick up clock_gettime())

The cost of a clock_gettime() (or of a gettimeofday()) can be a couple 
of microseconds on some systems, so it shouldnt be done too frequently.

Plus an absolute metric of "the whole workload took X.Y seconds" is 
useful too.

	Ingo