[Development] Slow speed of gcc compiled program under Kubuntu

[neo75]

Hello,
I faced following issue with slow speed under Kubuntu.

I have two OS on my PC with CPU Intel i7. One OS is Kubuntu 18.04, the other OS is Windows 10 Pro 1803 running on same HDD.

I have tested a simple program written in C language doing some number calculations.
On Kubuntu compiled with gcc 7.2.0, on Windows compiled with older gcc 5.2.0. under mingw-w64.

The result was amazing, running program was 5-times slower on Kubuntu, than on Windows.

I tried on Kubuntu to compile with some CPU specific options like -corei7 etc., but nothing helped.

Is there a reason for this slow speed under Kubuntu?

Thank you very much for any help.
Best Regards

[GreyGeek]

Depends on the libraries you load or which are loaded automatically. Floating point libraries are much slower than Integer libraries or BCD libraries.

[neo75]

Thanks for answer. On both systems I used compilation like this: "gcc -lm", so the library "math.h" should be loaded. The source code is exactly the same on both OS. Where could the mistake?

[GreyGeek]

Compile it with debug and then step through it using kdbg

[jlittle]

You haven't mentioned the optimization level used. That leads me to suspect the compiles have been done at different levels, which would produce a difference as you report.