注册 登录  
 加关注
   显示下一条  |  关闭
温馨提示!由于新浪微博认证机制调整,您的新浪微博帐号绑定已过期,请重新绑定!立即重新绑定新浪微博》  |  关闭

断尘居

温柔的男人像海洋。

 
 
 
 
 

日志

 
 

What's GC roots?  

2014-12-23 18:01:44|  分类: JVM/ HotSpot |  标签: |举报 |字号 订阅

  下载LOFTER 我的照片书  |

The so-called GC (Garbage Collector) roots are objects special for garbage collector. Garbage collector collects those objects that are not GC roots and are not accessible by references from GC roots.

There are several kinds of GC roots. One object can belong to more than one kind of root. The root kinds are:

  • Class - class loaded by system class loader. Such classes can never be unloaded. They can hold objects via static fields. Please note that classes loaded by custom class loaders are not roots, unless corresponding instances ofjava.lang.Class happen to be roots of other kind(s).
  • Thread - live thread
  • Stack Local - local variable or parameter of Java method
  • JNI Local - local variable or parameter of JNI method
  • JNI Global - global JNI reference
  • Monitor Used - objects used as a monitor for synchronization
  • Held by JVM - objects held from garbage collection by JVM for its purposes. Actually the list of such objects depends on JVM implementation. Possible known cases are: the system class loader, a few important exception classes which the JVM knows about, a few pre-allocated objects for exception handling, and custom class loaders when they are in the process of loading classes. Unfortunately, JVM provides absolutely no additional detail for such objects. Thus it is up to the analyst to decide to which case a certain "Held by JVM" belongs.

If an object is a root, it is specially marked in all views showing individual objects. For example, the following picture shows a fragment of paths view:



======================================
original: http://www.yourkit.com/docs/java/help/gc_roots.jsp

  评论这张
 
阅读(773)| 评论(0)
推荐 转载

历史上的今天

在LOFTER的更多文章

评论

<#--最新日志,群博日志--> <#--推荐日志--> <#--引用记录--> <#--博主推荐--> <#--随机阅读--> <#--首页推荐--> <#--历史上的今天--> <#--被推荐日志--> <#--上一篇,下一篇--> <#-- 热度 --> <#-- 网易新闻广告 --> <#--右边模块结构--> <#--评论模块结构--> <#--引用模块结构--> <#--博主发起的投票-->
 
 
 
 
 
 
 
 
 
 
 
 
 
 

页脚

网易公司版权所有 ©1997-2017