Also seeing 2 x quad-core system slower that 2 x dual core

Kris Kennaway kris at
Thu Nov 29 11:20:28 PST 2007

Matt Reimer wrote:
> On Nov 29, 2007 10:58 AM, Kris Kennaway <kris at> wrote:
>> Pete French wrote:
>>> On the dual core processors this takes about 20 seconds. On the quad
>>> cores it takes about 3 minutes! This is true for both the 32 and 64 bit
>>> versions of FreeBSD :-(
>> That almost certainly has nothing to do with how many CPUs your system
>> has, since rm -rf is a single process running on a single core.
> I wonder if I'm seeing this too. Running super-smack on a 2 x quad
> core 1.6GHz Dell 1950 I get about 40000 qps, whereas on a 2 x dual
> core 3.0GHz box I've seen 80000 qps.

Please, let's try to stay focused :)  rm -rf has nothing to do with 
super-smack and vice versa.

 > Is this expected?

It is not very surprising.  super-smack is not a good SMP benchmark, it 
does stupid things like 1-byte I/O, so it is not very scalable nor a 
good model of real-world database activity.  Accounting for your CPUs 
being twice as fast on the dual core, it roughly says that the benchmark 
is not scaling beyond 4 CPUs, which is in line with my own observations.


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