Linux 内核参数：min_free_kbytes
源码基于：Linux 5.4
针对节点 /proc/sys/vm/min_free_kbytes
0. 官方描述
/Documentation/admin-guide/sysctl/vm.rst
min_free_kbytes
===============This is used to force the Linux VM to keep a minimum number
of kilobytes free. The VM uses this number to compute a
watermark[WMARK_MIN] value for each lowmem zone in the system.
Each lowmem zone gets a number of reserved free pages based
proportionally on its size.Some minimal amount of memory is needed to satisfy PF_MEMALLOC
allocations; if you set this to lower than 1024KB, your system will
become subtly broken, and prone to deadlock under high loads.Setting this too high will OOM your machine instantly.
通过描述，该属性用以强制Linux VM 保留最小的free KB数，VM 通过该属性计算系统中每一个zone 的水位watermark[WMARK_MI