Not sure in what version the jvm.options file is introduced but is definitly 5.x and greater.
If you are on elasticsearch 5.x or greater why not use that file?
more /etc/elasticsearch/jvm.options
## JVM configuration
################################################################
## IMPORTANT: JVM heap size
################################################################
##
## You should always set the min and max JVM heap
## size to the same value. For example, to set
## the heap to 4 GB, set:
##
##
## See https://www.elastic.co/guide/en/elasticsearch/reference/current/heap-size.html
## for more information
##
################################################################
# Xms represents the initial size of total heap space
# Xmx represents the maximum size of total heap space
-Xms16g
-Xmx16g