Kernel-space memory layout

Kernel memory is managed in a straightforward way. It is not demand-paged, which means that for every allocation using kmalloc() or a similar function, there is real physical memory. Kernel memory is never discarded or paged out.

Some architectures show a summary of the memory mapping at boot time in the kernel log messages. This trace is taken from a 32-bit Arm device (a BeagleBone Black):

Memory: 511MB = 511MB total
Memory: 505980k/505980k available, 18308k reserved, 0K highmem
Virtual kernel memory layout:
    vector  : 0xffff0000 - 0xffff1000   ( 4 kB)
    fixmap  : 0xfff00000 - 0xfffe0000   ( 896 kB)
    vmalloc : 0xe0800000 - 0xff000000   ( 488 MB)
    lowmem  : 0xc0000000 - 0xe0000000   ( 512 MB)
    pkmap   : 0xbfe00000 - 0xc0000000   ( 2 MB)
    modules : 0xbf800000 - 0xbfe00000   ( 6 MB)
      .text : 0xc0008000 - 0xc0763c90   (7536 kB)
      .init : 0xc0764000 - 0xc079f700   ( 238 kB)
      .data : 0xc07a0000 - 0xc0827240   ( 541 kB)
...