title: Calling msync Necessary?
body: <p>After reading few articles and posts:
  <a href="https://lwn.net/Articles/502612/" rel="nofollow noreferrer">https://lwn.net/Articles/502612/</a>
  <a href="https://stackoverflow.com/questions/26097316/mmap-msyncms-async-and-munmap">mmap, msync(MS_ASYNC) and munmap</a></p>
  
  <p>I am kind of confused:<br/>
  1. whether msync really does anything (2nd link above includes a section of a manpage to indicate it doesn't in newer kernels; tho, the first link says it does do something)<br/>
  2. whether calling msync is necessary if a process might get killed or crashed (but not the OS).<br/>
  3. how frequent does the kernel flush the mmapped memory back to the "disk"?</p>
  
  <p>Let's say I use kernel 3.10 and 2.6.32.</p>
  
  <p>Thanks.</p>