Commits on Mar 13, 2018

1. fix: disable swap for executor_linux allocations …

   A comment in the nomad source code states that swapping for
   executor_linux allocations is disabled but it wasn't.
   
   Nomad wrote -1 to the memsw.limit_in_bytes cgroup file to disable
   swapping.
   This has the following problems:
   
   1.) Writing -1 to the file does not disable swapping. It sets
       the limit for memory and swap to unlimited.
   2.) On common Linux distributions like Ubuntu 16.04 LTS the
       memsw.limit_in_bytes cgroup file does not exist by default.
       The memsw.limit_in_bytes file only exist if the Linux kernel is
       build with CONFIG_MEMCG_SWAP=yes and either
       CONFIG_MEMCG_SWAP_ENABLED=yes or when the kernel parameter
       swapaccount=1 is passed during boot.
       Most Linux distributions disable swap accounting by default because
       of higher memory usage.
       Nomad silently ignores if writing to the memsw.limit_in_bytes file
       fails. The allocation succeeds, no message is logged to notify the
       user.
   
   To ensure that disabling swap works on common Linux kernels, disable
   swapping by writing 0 to the memory.swappiness file.
   Using the memory.swappiness file only requires that the kernel is
   compiled with CONFIG_MEMCG=yes. This is the default in common Linux
   kernels.

   

   fho committed Mar 13, 2018
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2. Add #3958 to changelog

   

   schmichael committed Mar 13, 2018
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