Linux, FreeBSD, Solaris i7-3960X Scaling Performance

[phoronix]

Phoronix: Linux, FreeBSD, Solaris i7-3960X Scaling Performance

Using the new Intel Core i7 3960X Extreme Edition Sandy Bridge processor, Scientific Linux 6.1, Debian GNU/Linux, Debian GNU/kFreeBSD, and Solaris 11 11/11 were benchmarked when having a different number of CPU cores enabled to see how well each operating system scales up to six cores plus Hyper Threading.

http://www.phoronix.com/vr.php?view=16848

[birdie]

Michael,

"Time to compile" - "more is better" - really? WTF?

[Michael]

Michael,

"Time to compile" - "more is better" - really? WTF?

All results are normalized as said in the article so on those graphs, yes, better is faster.

[liam]

Check out the Phong rendering graph.

Is solaris scaling TOO well here?
At the 2 core mark it looks like it is above 2 times better.
I suppose the code could be written in such a way that it has too much overhead for small number of processors, but does anyone have any experience writing superscalable code that can say for sure?

[ttsiodras]

Re: Check out the Phong rendering graph

(Disclaimer: I am the author of the renderer)

Indeed, I noticed that in the graph, too - but there's a simple explanation.
The renderer is using simple OpenMP loops, of the form:

#ifdef USE_OPENMP
#pragma omp parallel for
#endif
// Plot all the vertices of object i on the canvas
for(int j=0; j<(int)_vertices.size(); j++) {

...so no, in theory it is impossible to see a speedup of more than 2x when using 2 threads instead of one - or a speedup of more than 4x when using 4 threads.

Unless... the single-core case is handled BADLY by Solaris.

Michael plotted the relative speedup when going from one core to 2, 4, 6, etc.
In this case, the single-core running speed of Solaris ( as reported in the full benchmark results) is 21.06 frames per second, when Linux scored around 28 frames per second - in both cases, using a single core!

So, in effect, what we are seeing here is that Solaris is "punishing" single-core executions - i.e. the OpenMP library in Solaris handles single-core machines very badly.

P.S. Perhaps this affected other benchmarks too - it's easy for Solaris to appear to have better scalability, when the single-core performance is much worse than the other contenders (Linux and BSD in this case). For example, look at the speed of C-Ray when run with a single core under Solaris vs the other two (Linux/BSD) - it is about half as much (250 seconds vs 500 seconds). Solaris "punishes" single-core executions so much, that it appears to scale much better as more cores are introduced...

Thanassis.