Add an option "cgroup_nodelete" to not delete cgroups after job completion

o Add an option cgroup_nodelete to not remove cgroups created by fio after
  the job completion. This can help a user in inspecting various cgroup
  files after fio job completion.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fio.1 b/fio.1
index 5d0988b..12146c8 100644
--- a/fio.1
+++ b/fio.1
@@ -762,6 +762,12 @@
 Set the weight of the cgroup to this value. See the documentation that comes
 with the kernel, allowed values are in the range of 100..1000.
 .TP
+.BI cgroup_nodelete \fR=\fPbool
+Normally fio will delete the cgroups it has created after the job completion.
+To override this behavior and to leave cgroups around after the job completion,
+set cgroup_nodelete=1. This can be useful if one wants to inspect various
+cgroup files after job completion. Default: false
+.TP
 .BI uid \fR=\fPint
 Instead of running as the invoking user, set the user ID to this value before
 the thread/process does any work.