Knoppix V6.7.1

[ruymbeke]

Hello,
Does anyone know why compiling a source tree as "root" is much slower than as the default "Knoppix" user ?
(by just using "su" before starting the make). Top indicates a much higher percentage of system call (%sy)
with root than Knoppix and as such there is not much time left for the user apps (%us). Any idea how to fix it ?
(I know it is usually a bad idea to compile as root anyway but in some cases root is required...)
Thanks,
Gilles

[kl522]

Hello,
Does anyone know why compiling a source tree as "root" is much slower than as the default "Knoppix" user ?
(by just using "su" before starting the make). Top indicates a much higher percentage of system call (%sy)
with root than Knoppix and as such there is not much time left for the user apps (%us). Any idea how to fix it ?
(I know it is usually a bad idea to compile as root anyway but in some cases root is required...)
Thanks,
Gilles

Personally I am not so convinced that compiling things as root will be slower, unless the makefiles do additional things when detecting compiling as root verses normal users. In any case, if one compiles something repeatedly, the speed can be improved by installing/configuring 'ccache'. Therefore if compile as root is indeed slower, perhaps the cache has not been setup for 'root' ? It's easy to verify that, just check if there is a .ccache folder for /home/knoppix. If the folder exists, meaning likely you have been using ccache without realizing it.

[ruymbeke]

Hi Kl522,
I do run my test both with and without ccache. As expected, running twice or more with ccache provides some speed improvement.
But at this point I do not care much about ccache. The problem that I try to understand is the time difference when compiling as root
or as the knoppix user. Or in other words, in both cases (with or without ccache) running as root is much slower than with the user Knoppix.
Thanks for your help. Best Regards,
Gilles

[kl522]

The problem that I try to understand is the time difference when compiling as root
or as the knoppix user. Or in other words, in both cases (with or without ccache) running as root is much slower than with the user Knoppix.

Without disclosing any of your proprietary work/sources, are you able to provide with a test-case of compiling as root is slower than compiling as knoppix user ?