Date: Wed, 13 Sep 2006 13:00:25 -0400 From: Mike Meyer <mwm-keyword-freebsdhackers2.e313df@mired.org> To: Danny Braniss <danny@cs.huji.ac.il> Cc: freebsd-hackers@freebsd.org Subject: Re: numbers don't lie ... Message-ID: <17672.14633.859999.417883@bhuda.mired.org> In-Reply-To: <E1GNOLq-000DC2-1Q@cs1.cs.huji.ac.il> References: <E1GNOLq-000DC2-1Q@cs1.cs.huji.ac.il>
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In <E1GNOLq-000DC2-1Q@cs1.cs.huji.ac.il>, Danny Braniss <danny@cs.huji.ac.il> typed:
> Im testing these 2 boxes, Sun X4100 and Dell-2950, and:
>
> SUN X4100: Dual Core AMD Opteron(tm) Processor 280 (2393.19-MHz K8-class CPU)
> one 70g sata disk
> DELL 2950: Intel(R) Xeon(TM) CPU 3.20GHz (3192.98-MHz K8-class CPU)
> 4 sata disks + raid0
>
> they both run identical 6.1-STABLE.
>
> my 'cpu benchmark' shows the amd being much better than the intel.
> but, doing a make buildworld give interesting results:
>
> dell-2950 : make -j16 TARGET_ARCH=amd64 buildworld : 24m17.41s real 1h3m3.26s
> user 17m15.07s sys
> dell-2950 : make -j8 TARGET_ARCH=amd64 buildworld : 24m8.28s real 1h2m59.38s
> user 16m16.20s sys
>
> sunfire : make -j16 TARGET_ARCH=amd64 buildworld : 24m21.38s real 49m6.68s
> user 14m22.64s sys
> sunfire : make -j8 TARGET_ARCH=amd64 buildworld : 23m47.69s real 48m53.58s
> user 13m44.81s sys
>
> which probably says something about my 'cpu benchmark' :-(
Yes - that it's not very good at predicting performance on a parallel
make. That's not surprising, as it's true of most benchmarks. You
might want to check out some of the benchmarks in the ports tree as
well.
> but why is the user time so much different between the boxes?
What's the CPU configuration? The AMD is dual core - is that it? Could
the Xeon be dual-core and hyperthreaded, so it's got that many more
CPUs to contribute towards user time?
To illustrate, I have numbers for "make -j4" for a P4 with and without
hyperthreading enabled:
machdep.hyperthreading_allowed: 1 -> 0
50m55.99s real 35m28s.19 user 8m20s.02 sys
machdep.hyperthreading_allowed: 0 -> 1
38m48s.85 real 55m2s.43 user 12m27s.90 sys
Note the effect of the second CPU on the user time.
<mike
--
Mike Meyer <mwm@mired.org> http://www.mired.org/consulting.html
Independent Network/Unix/Perforce consultant, email for more information.
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