Re: More kernel performance tests on FreeBSD 10.0-CURRENT

On Fri, Sep 21, 2012 at 11:39:40PM +0200, Dimitry Andric wrote:
> Hi all,
> 
> As a followup to my previous post about the performance of FreeBSD 10.0
> kernels compiled with different compilers (clang and gcc), I did another
> series of tests, now on a more modern machine (Core i5-based).  I also
> tested the performance with different compiler optimization settings.
> 
> The attached text file[1] contains more information about these tests,
> performance data, and my conclusions.  Any errors and omissions are also
> my fault, so if you notice them, please let me know.
> 
> The executive summary: GENERIC kernels compiled with clang 3.2 are again
> a little faster than those compiled with gcc 4.2.1.  For gcc, compiling
> with -O2 also gives a slightly faster kernel than with -O1, but for
> clang there is no measurable difference between those flags.
> 
> Again, many thanks to Gavin Atkinson for providing the required
> hardware.
...

> Conclusion:
> -----------
> Kernels compiled with clang are a little faster in real time for building world,
> and in system time the difference is even larger, roughly 10%.  For clang, the
> difference between -O1 and -O2 is not measurable, but for gcc, -O2 is slightly
> faster than -O1.
> 

Thank you very much for finishing the initial assessment.
In my opinion, this positively closes the issue of the uncertainicity
of the performance impact of the proposed clang use by default for the
base system.

Now, if only ports were handled.