title: memory mapped files system call - linux
body: <p>When we map a file to memory, a system call is required. Do subsequent accesses to the file require system calls or is the virtual memory page of the process mapped to the actual page cache in memory?</p>
  
  <p><strong>update</strong>:
  what i also want to know is that if multiple processes are accessing the same file through mmap. they will be accessing the same physical memory portion write.</p>