Zone watermarks

Zone watermarks

quoted from : Professional Linux kernel architecture by Wolfgang Mauerer

page 144

Before calculating the various watermarks (pages_low, pages_high, pages_min ), the kernel first determines the minimum memory space that must remain free for critical allocations.

This is stored in the global variable min_free_kbytes.

cat /proc/sys/vm/min_free_kbytes

init_per_zone_pages_min()
setup_per_zone_pages_min()
setup_per_zone_lowmem_reserve()