[ltt-dev] Experiments on CPU time statistics

[Francis Giraldeau]

Mathieu Desnoyers <compudj at krystal.dyndns.org> a écrit :
>> =================================================
>> trace-bonnie.sh : start bonnie++ process for 10s
>>
>> time statistics:
>> real	0m10.715s
>> user	0m0.420s
>> sys	0m6.350s
>>
>>
>> lttv statistics:
>> events count        : 11088588
>> cpu time            : 80.051904112
>
> cpu time should be good. How many cores does you machine have ? 8 ?

Thanks for explainations. Yes, the system has 8 cores. The maximum CPU  
time for 1 second is hence 8 seconds.

>> =================================================
>> sleep 1s : start a sleep of 1s
>>
>> time statistics:
>> real	0m1.002s
>> user	0m0.000s
>> sys	0m0.000s
>>
>>
>> lttv statistics:
>> cpu time            : 7.841686487

How then can we explain that on an idle system, the CPU time is yet  
(almost) the number of CPUs times the trace duration?

Cheer,

Francis