anchor.diff:  === Disable swapping
   
   Most operating systems try to use as much memory as possible for file system
  -caches and eagerly swap out unused application memory. This can result in
  -parts of the JVM heap being swapped out to disk.
  +caches and eagerly swap out unused application memory. This can result in parts
  +of the JVM heap or even its executable pages being swapped out to disk.
   
  -Swapping is very bad for performance and for node stability and should be
  -avoided at all costs. It can cause garbage collections to last for **minutes**
  -instead of milliseconds and can cause nodes to respond slowly or even to
  -disconnect from the cluster.
  +Swapping is very bad for performance, for node stability, and should be avoided
  +at all costs. It can cause garbage collections to last for **minutes** instead
  +of milliseconds and can cause nodes to respond slowly or even to disconnect
  +from the cluster. In a resilient distributed system, it's more effective to let
  +the operating system kill the node.
   
  -There are three approaches to disabling swapping:
  +There are three approaches to disabling swapping. The preferred option is to
  +completely disable swap. If this is not an option, whether or not to prefer
  +minimizing swappiness versus memory locking is dependent on your environment.
  +
  +[[disable-swap-files]]
  +==== Disable all swap files
  +
  +Usually Elasticsearch is the only service running on a box, and its memory usage
  +is controlled by the JVM options. There should be no need to have swap enabled.
  +
  +On Linux systems, you can disable swap temporarily by running:
  +
  +[source,sh]
  +--------------
  +sudo swapoff -a
  +--------------
  +
  +To disable it permanently, you will need to edit the `/etc/fstab` file and
  +comment out any lines that contain the word `swap`.
  +
  +On Windows, the equivalent can be achieved by disabling the paging file entirely
  +via `System Properties → Advanced → Performance → Advanced → Virtual memory`.
  +
  +[[swappiness]]
  +==== Configure `swappiness`
  +
  +Another option available on Linux systems is to ensure that the sysctl value
  +`vm.swappiness` is set to `1`. This reduces the kernel's tendency to swap and
  +should not lead to swapping under normal circumstances, while still allowing the
  +whole system to swap in emergency conditions.
   
   [[mlockall]]
   ==== Enable `bootstrap.memory_lock`
   
  -The first option is to use
  -http://opengroup.org/onlinepubs/007908799/xsh/mlockall.html[mlockall] on Linux/Unix systems, or https://msdn.microsoft.com/en-us/library/windows/desktop/aa366895%28v=vs.85%29.aspx[VirtualLock] on Windows, to
  -try to lock the process address space into RAM, preventing any Elasticsearch
  -memory from being swapped out.  This can be done, by adding this line
  -to the `config/elasticsearch.yml` file:
  +Another option is to use
  +http://opengroup.org/onlinepubs/007908799/xsh/mlockall.html[mlockall] on
  +Linux/Unix systems, or
  +https://msdn.microsoft.com/en-us/library/windows/desktop/aa366895%28v=vs.85%29.aspx[VirtualLock]
  +on Windows, to try to lock the process address space into RAM, preventing any
  +Elasticsearch memory from being swapped out. This can be done, by adding this
  +line to the `config/elasticsearch.yml` file:
   
   [source,yaml]
   --------------
   bootstrap.memory_lock: true
   --------------
   
  -WARNING: `mlockall` might cause the JVM or shell session to exit if it tries
  -to allocate more memory than is available!
  +WARNING: `mlockall` might cause the JVM or shell session to exit if it tries to
  +allocate more memory than is available!
   
   After starting Elasticsearch, you can see whether this setting was applied
   successfully by checking the value of `mlockall` in the output from this
  
positive.code: // CONSOLE
  
  If you see that `mlockall` is `false`, then it means that the `mlockall`
  request has failed.  You will also see a line with more information in the
  logs with the words `Unable to lock JVM Memory`.
  
  The most probable reason, on Linux/Unix systems, is that the user running
  Elasticsearch doesn't have permission to lock memory.  This can be granted as follows:
  
  `.zip` and `.tar.gz`::
  
  
negative.code: --------------
  
  or setting this JVM flag in the jvm.options configuration file.
  