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如何剖析Java中的对象创建？

[英]How to profile object creation in Java?

原文 2010-03-16 18:29:21 1 4 java/ performance/ garbage-collection

The system I work with is creating a whole lot of objects and garbage collecting them all the time which results in a very steeply jagged graph of heap consumption. 我正在使用的系统正在创建大量对象并一直对其进行垃圾收集，这导致了堆消耗的锯齿状曲线。 I would like to know which objects are being generated to tune the code, but I can't figure out a way to dump the heap at the moment the garbage collection starts. 我想知道正在生成哪些对象来优化代码，但是在垃圾回收开始时，我想不出一种方法来转储堆。 When I tried to initiate dumpHeap via JConsole manually at random times, I always got results after GC finished its run, and didn't get any useful data. 当我尝试通过JConsole手动手动启动dumpHeap时，我总是在GC完成运行后得到结果，而没有得到任何有用的数据。

Any notes on how to track down excessive temporary object creation are welcome. 欢迎提供有关如何追踪过多临时对象创建的任何注释。

4 个解决方案

What you're looking for are the most intensive allocation sites in your program. 您正在寻找的是程序中最密集的分配站点。 You can use a tool like: Allocation Instrumentor for Java . 您可以使用以下工具： Java分配工具。 The answer to your comment: 您的评论的答案：

When I tried to initiate dumpHeap via JConsole manually at random times, I always got results after GC finished its run, and didn't get any useful data. 当我尝试通过JConsole手动手动启动dumpHeap时，我总是在GC完成运行后得到结果，而没有得到任何有用的数据。

is that a heap dump triggers a GC in the VM because the heap dump is a report of what is live in the heap (for the most part) - the VM wants the most accurate picture of what is live at the time the heap dump was triggered and therefore a GC event will always happen right after the dump request is initiated. 的原因是堆转储会触发VM中的GC，因为堆转储是（大部分情况下）堆中活动内容的报告-VM希望获得堆转储时活动内容的最准确信息触发，因此GC事件将始终在启动转储请求后立即发生。

Tuning the Java heap is an art - and there is plenty of material out on the web on how to do it. 调优Java堆是一门艺术-网上有很多关于如何做到这一点的资料。

看一下BTrace可以做什么（ http://kenai.com/projects/btrace/pages/Home ），或者尝试在JDK 6u18中使用jvisualvm进行实时内存采样。

Apache JMeter Apache JMeter

Quote from the projects page: 从项目页面引用：

Apache JMeter may be used to test performance both on static and dynamic resources (files, Servlets, Perl scripts, Java Objects, Data Bases and Queries, FTP Servers and more). Apache JMeter可用于测试静态和动态资源（文件，Servlet，Perl脚本，Java对象，数据库和查询，FTP服务器等）的性能。 It can be used to simulate a heavy load on a server, network or object to test its strength or to analyze overall performance under different load types. 它可用于模拟服务器，网络或对象上的重负载，以测试其强度或分析不同负载类型下的整体性能。

I remember M. Fowler mentioned that it's almost impossible to guess what causes performance issues until you test the whole system with a profiler. 我记得M. Fowler提到过几乎不可能猜测导致性能问题的原因，除非您使用探查器测试整个系统。

You could use the JVMPI interface (and tools like Dr.MEM) and create your own custom solution if non of the solutions prescribed above solve your purpose. 如果以上规定的解决方案均无法解决您的目的，则可以使用JVMPI接口（和Dr.MEM等工具）并创建自己的自定义解决方案。 This could however be an overkill depending on your problem. 但是，根据您的问题，这可能是一个过大的杀伤力。