Better performance when CONFIG_DEBUG_KERNEL is on

[Jean-Michel Hautbois]

Hi everybody,

I am using a mpc5200 chip with a linux 2.6.33.7-rt29.
I am using the ELDK toolchain :

ppc_6xx-gcc -v

Target: powerpc-linux
Configured with:
/opt/eldk/build/ppc-2008-04-01/work/usr/src/denx/BUILD/crosstool-0.43/build/gcc-4.2.2-glibc-20070515T2025-eldk/powerpc-linux/gcc-4.2.2/configure
--target=powerpc-linux --host=i686-host_pc-linux-gnu
--prefix=/var/tmp/eldk.UZpAG7/usr/crosstool/gcc-4.2.2-glibc-20070515T2025-eldk/powerpc-linux
--disable-hosted-libstdcxx
--with-headers=/var/tmp/eldk.UZpAG7/usr/crosstool/gcc-4.2.2-glibc-20070515T2025-eldk/powerpc-linux/powerpc-linux/include
--with-local-prefix=/var/tmp/eldk.UZpAG7/usr/crosstool/gcc-4.2.2-glibc-20070515T2025-eldk/powerpc-linux/powerpc-linux
--disable-nls --enable-threads=posix --enable-symvers=gnu
--enable-__cxa_atexit --enable-languages=c,c++,java --enable-shared
--enable-c99 --enable-long-long --without-x
Thread model: posix
gcc version 4.2.2

When I have the CONFIG_DEBUG_KERNEL flag, the latencies I am mesuring
are better than when the flag is off.
And the jitter is lower...

I must tell I am confused. I have no explanation about that, except
maybe optimisations which would be different when the -g flag is
added...

If any of you has an idea, I am looking forward for your response :).

Thanks in advance,
Best Regards.
JM