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

[Matt Reimer]

On Nov 29, 2007 11:20 AM, Kris Kennaway <kris at freebsd.org> wrote:
> Matt Reimer wrote:
> > On Nov 29, 2007 10:58 AM, Kris Kennaway <kris at freebsd.org> 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.

It's relevant to $subject.

>  > 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.

Is sysbench a better benchmark? It gives me 2362.99 on the 2 x
dual-core box vs 1327.26 on the 2 x quad-core box.

Matt