Merge pull request #2427 from hashicorp/f-gc-limit

Limit parallelism during garbage collection

website/source/docs/agent/configuration/client.html.md

@@ -92,6 +92,10 @@ client {
 - `gc_inode_usage_threshold` `(float: 70)` - Specifies the inode usage percent
   which Nomad tries to maintain by garbage collecting terminal allocations.
 
+- `gc_parallel_destroys` `(int: 2)` - Specifies the maximum number of
+  parallel destroys allowed by the garbage collector. This value should be
+  relatively low to avoid high resource usage during garbage collections.
+
 - `no_host_uuid` `(bool: false)` - Force the UUID generated by the client to be
   randomly generated and not be based on the host's UUID.