执行 rake sunspot:solr:start 时出错，提示如下：

Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
Removing stale PID file at /var/www/poiop/solr/pids/development/sunspot-solr-development.pid
Successfully started Solr ...

执行 java -version 后显示如下：

java version "1.7.0_03"
Java(TM) SE Runtime Environment (build 1.7.0_03-b04)
Java HotSpot(TM) Client VM (build 22.1-b02, mixed mode)

执行 free -m 后显示如下：

             total       used       free     shared    buffers     cached
Mem:           512        224        287          0          0          0
-/+ buffers/cache:        224        287
Swap:            0          0          0

希望得到大家的帮助