Performance of 4.x vs 5.x (nbench results)

Matthias Buelow mkb at
Tue May 24 14:09:35 PDT 2005

> Well, that's hardly surprising.. short of minimizing the number of page
> faults and avoiding TLB/cache shootdowns, what can the OS do to speed up
> the CPU pipeline?  The nbench program doesn't benchmark any OS functions
> at all (except for loading time).

Btw., what these programs aren't completely nonsense, what they are good
for is stuff like finding out that the G5 processor in an 1.6ghz iMac
has about 1/3 faster floating point performance than a 3ghz pentium-4
(but somewhat lower integer and memory performance). However, it doesn't
show that for certain workloads the p4 I tested is much faster than the
particular g5 iMac, since it's got double the amount of 2nd level cache
(1mb vs. 512K). So the results are always very special and say very
little about allround performance. (For example, for numerical stuff,
the iMac would be the better choice, except if you have workloads which
benefit significantly from a larger cache.)


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