myeclipse的tomcat启动不起来，但myeclipse自带的tomcat能启动我的项目

java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:303)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:431)
Exception in thread "main" java.lang.OutOfMemoryError: PermGen space
at java.lang.Throwable.getStackTraceElement(Native Method)
at java.lang.Throwable.getOurStackTrace(Throwable.java:591)
at java.lang.Throwable.printStackTraceAsCause(Throwable.java:481)
at java.lang.Throwable.printStackTrace(Throwable.java:468)
at java.lang.Throwable.printStackTrace(Throwable.java:451)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:445)

我机子装了tomcat 7 ,tomcat无项目部署时，启动无误，但一部署就报这个错