From: compudj@krystal.dyndns.org (Mathieu Desnoyers)
Subject: [ltt-dev] Experiments on CPU time statistics
Date: Thu, 11 Nov 2010 13:59:44 -0500 [thread overview]
Message-ID: <20101111185944.GA27102@Krystal> (raw)
In-Reply-To: <20101111125029.18064gu6bt6eo084@www.usherbrooke.ca>
* Francis Giraldeau (Francis.Giraldeau at USherbrooke.ca) wrote:
> Hi,
>
> I'm doing some experiments with CPU statistics, and I think that those
> computed by lttv are wrong. I did 3 tests, and for each command the time
> utility was used to get a baseline, and the command has been run between
> lttctl -C and lttctl -D to get a tight window around the test process.
>
> =================================================
> 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 ?
>
> elapsed time? : 544.593369365
Elapsed time is the total of the per-thread elapsed time I think (it's
really been a while since I played with this code though). It would make
sense if you have 54 threads in your system.
I don't have entire confidence that the elapsed time is correct.
>
> cumulative cpu time : 6.747053976
cumulative cpu time is known to be wrong.
Thanks,
Mathieu
>
> =================================================
> sleep 1s : start a sleep of 1s
>
> time statistics:
> real 0m1.002s
>
> user 0m0.000s
>
> sys 0m0.000s
>
>
> lttv statistics:
> events count : 94929
>
>
> cpu time : 7.841686487
>
> elapsed time : 34.566952675
>
> cumulative cpu time : 0.036465023
>
>
> =================================================
> trace-burn.sh 1s * 8 process simultan?s
>
> time statistics:
> real 0m1.031s
>
> user 0m7.650s
>
> sys 0m0.020s
>
>
> lttv statistics:
> events count : 95402
>
> cpu time : 8.584145675
>
> elapsed time : 33.845893813
>
> cumulative cpu time : 0.037255816
> =================================================
>
> I was expecting lttv enlapsed time to be close to real time, lttv
> cumulative cpu time to be greater or equal to lttv cpu time, and lttc
> cpu time to match user + sys time. Does it make sens, or maybe I'm
> getting something wrong?
>
> Cheer,
>
> Francis
>
>
> _______________________________________________
> ltt-dev mailing list
> ltt-dev at lists.casi.polymtl.ca
> http://lists.casi.polymtl.ca/cgi-bin/mailman/listinfo/ltt-dev
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2010-11-11 18:59 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-11 17:50 Francis Giraldeau
2010-11-11 18:59 ` Mathieu Desnoyers [this message]
2010-11-11 19:23 ` Michel Dagenais
2010-11-11 21:05 ` Francis Giraldeau
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