I tried to setting ES_HEAP_SIZE to 1024m on my linux server. I used this setting > export ES_HEAP_SIZE=1024m. Now how to check if this new setting is work??
Look at the resulting JVM process when you start ES, specifically the -Xmx option.
If you're starting ES as a service (which you should be doing) you should probably be modifying /etc/sysconfig/elasticsearch or /etc/default/elasticsearch instead.