内核kernel参数
Linux下有3个特殊的进程，idle进程(PID = 0), init进程(PID = 1)和kthreadd(PID = 2)
内核初始化rest_init函数中，由进程 0 (swapper 进程)创建了两个process
init 进程 (pid = 1, ppid = 0)
kthreadd (pid = 2, ppid = 0)
所有其它的内核线程的ppid 都是 2，也就是说它们都是由kthreadd thread创建的
vm.max_map_count
1 | sysctl -w vm.max_map_count=262144 |
Elasticsearch uses a mmapfs directory by default to store its indices. The default operating system limits on mmap counts is likely to be too low, which may result in out of memory exceptions.
mmapfs
The MMap FS type stores the shard index on the file system (maps to Lucene MMapDirectory) by mapping a file into memory (mmap). Memory mapping uses up a portion of the virtual memory address space in your process equal to the size of the file being mapped. Before using this class, be sure you have allowed plenty of virtual address space.
