Kernel space memory layout

Kernel memory is managed in a fairly 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) 
   ...