Re: More kernel performance tests on FreeBSD 10.0-CURRENT

Am 09/21/12 23:39, schrieb Dimitry Andric:
> 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.
> 
> -Dimitry
> 
> [1]: Also available at:
> <http://www.andric.com/freebsd/perftest/perftest-kernel-2012-09-21a.txt>


At least one can say FreeBSD does not suffer from performance drain
using the cutting edge clang 3.2 compared with a gcc 4.2.1 compiler, the
echo from the past.

Dimirty, are you planning also to benchmark clang 3.2 versus gcc 4.8.0?
From the development point of view, such a benchmark would be more
natural, but I do not know whether the kernel sources are gcc
4.8-friendly and would allow such a test.

What is about optimization level "-O3" and architectural recognition via
"-march=native"?

Neverthelesse, thanks.

oh