Huge difference in reserved memory - how to find?

[Erik Rull]

Dear all,

I'm trying to move from 3.4.67 to 4.19 on a rather old Intel CPU and run into
some memory trouble I do not understand:

The point that confuses me is the difference in the following line:

3.4.67:
[    0.000000] Memory: 235736k/261056k available (4695k kernel code, 24872k
reserved, 2889k data, 564k init, 0k highmem)

4.19.82-rt30:
[    0.534687] Memory: 165244K/260668K available (9050K kernel code, 821K
rwdata, 2500K rodata, 808K init, 440K bss, 95424K reserved, 0K cma-reserved, 0K
highmem)

Why is so much memory reserved in the 4.19? I would like to understand why and
how I could reduce that. I need some more space on the system to let my
application run.

Thanks a lot!

Best regards,

Erik