title: How to get system page size in OCaml
body: <p>I have searched in modules <code>Sys</code>, <code>Gc</code>, and <code>Unix</code>, but did not find a means to get the system page size in OCaml. How can we get the system page size?</p>
  
  <p>I have OCaml 4.06 and macOS 10.12.6 (Sierra)</p>