为了确定下一次重新部署后jvm是否可能会出现permgen空间不足的情况，我想在操作之前监视当前的permgen空间使用情况

就像是：

set myPermGenThreshold = 0.51  (51%)
currentlyUsedPermGenSize = (...ask the jvm here... say it's 0.6)

if (currentlyUsedPermGenSize > myPermGenThreshold ) {
 (...restart tomcat...)
}
else {
  (...redeploy application...)
}