title: Native memory allocation (mmap) failed to map
body: <p>I have started facing Native memory allocation issue. I guess could be related with the -Xmx and -Xms settings. What is the recommended way to set this values ?</p>
  
  <p>Currently I have: -Xmx13G -Xms6G </p>
  
  <p>I read that is recommended to set same values but without any explanation of why.</p>
  
  <p>The error I am getting is :</p>
  
  <pre><code>    # There is insufficient memory for the Java Runtime Environment to continue.
  # Native memory allocation (mmap) failed to map 746061824 bytes for committing reserved memory.
  # Possible reasons:
  #   The system is out of physical RAM or swap space
  #   In 32 bit mode, the process size limit was hit
  #   Decrease number of Java threads
  #   Decrease Java thread stack sizes (-Xss)
  #   Set larger code cache with -XX:ReservedCodeCacheSize=
  # This output file may be truncated or incomplete.
  #
  #  Out of Memory Error (os_linux.cpp:2627), pid=13528, tid=0x00007f2b0b5f5700
  #
  # JRE version: Java(TM) SE Runtime Environment (8.0_101-b13) (build 1.8.0_101-b13)
  # Java VM: Java HotSpot(TM) 64-Bit Server VM (25.101-b13 mixed mode linux-amd64 compressed oops)
  # Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
  #
  
  /proc/meminfo:
  MemTotal:       16433112 kB
  MemFree:          166336 kB
  Buffers:          114324 kB
  Cached:           398396 kB
  SwapCached:            0 kB
  Active:         15151496 kB
  Inactive:         254348 kB
  Active(anon):   14893020 kB
  Inactive(anon):      604 kB
  Active(file):     258476 kB
  Inactive(file):   253744 kB
  Unevictable:           0 kB
  Mlocked:               0 kB
  SwapTotal:             0 kB
  SwapFree:              0 kB
  Dirty:                12 kB
  Writeback:             0 kB
  AnonPages:      14892976 kB
  Mapped:            24024 kB
  Shmem:               696 kB
  Slab:             349384 kB
  SReclaimable:     187700 kB
  SUnreclaim:       161684 kB
  KernelStack:       43520 kB
  PageTables:       276768 kB
  NFS_Unstable:          0 kB
  Bounce:                0 kB
  WritebackTmp:          0 kB
  CommitLimit:     8216556 kB
  Committed_AS:   33089080 kB
  VmallocTotal:   34359738367 kB
  VmallocUsed:       31404 kB
  VmallocChunk:   34359652884 kB
  HardwareCorrupted:     0 kB
  AnonHugePages:  13486080 kB
  HugePages_Total:       0
  HugePages_Free:        0
  HugePages_Rsvd:        0
  HugePages_Surp:        0
  Hugepagesize:       2048 kB
  DirectMap4k:       28672 kB
  DirectMap2M:    16879616 kB
  
  Memory: 4k page, physical 16433112k(166336k free), swap 0k(0k free)
  
  vm_info: Java HotSpot(TM) 64-Bit Server VM (25.101-b13) for linux-amd64 JRE (1.8.0_101-b13), built on Jun 22 2016 02:59:44 by "java_re" with gcc 4.3.0 20080428 (Red Hat 4.3.0-8)
  </code></pre>