Kernel free memory control / pressure

[Slawa Olhovchenkov]

I am looked to code control kernel free memory /p ressure and see some
strange points:

- vm.v_free_target is RW but do nothing. You can set it to any value
  and this is don't have any effect.
- vmd_free_target (as vm.domain.N.stats.free_target) is RD and don't
  have any sysctl to tune

Same for v_free_min, v_free_reserved, v_pageout_free_min.

As I see this behavior for 12 and current branches, after-NUMA
kernels.

Is this expected behavior?

PS:

(kgdb) p vm_dom[0].vmd_page_count
$2 = 33454844
(kgdb) p vm_dom[1].vmd_page_count
$3 = 31872620

What source of  vm_dom[0].vmd_page_count > vm_dom[1].vmd_page_count?