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Re:内存使用情况，怪现象！ [Re:windshome]

JiafanZhou

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发贴: 736
积分: 61

于 2008-09-10 19:31

I think it is called "Young generation and the Tenured generation", see the link below:
http://java.sun.com/docs/hotspot/gc1.4.2/faq.html

I am not familiar with the Garbage Collection, but some points from the document above seems suspicious and might be related to your issue here.

1. How is the generational collector implemented in HotSpot(tm)?

The default collector in HotSpot has two generations: the young generation and the tenured generation. Most allocations are done in the young generation. The young generation is optimized for objects that have a short lifetime relative to the interval between collections. Objects that survive several collections in the young generation are moved to the tenured generation. The young generation is typically smaller and is collected more often. The tenured generation is typically larger and collected less often.

11. What is the best size for the young generation?

The young generation should be sized large enough so that short-lived objects have a chance to die before the next young generation collection. This is a tradeoff since a larger young generation will allow more time for objects to die but may also take longer to collect. Experiment with the size of the young generation to optimize the young generation collection time or the application throughput.

12. What should I do if my application has mid- or long-lived objects?

Objects that survive a young generation collection have a copying cost (part of the algorithm for a young generation collection is to copy any objects that survive). Mid- or long-lived objects may be copied multiple times. Use the -XX option MaxTenuringThreshold to determine the copying costs. Use -XX:MaxTenuringThreshold=0 to move an object that survives a young generation collection immediately to the tenured generation. If that improves the performance of the application, the copying of long-lived objects is significant. Note that the throughput collector does not use the MaxTenuringThreshold parameter.

When I was a kid I used to pray every night for a new bike. Then I realized that The Lord doesn't work that way, so I stole one and asked him to forgive me.

话题树型展开

人气	标题	作者	字数	发贴时间
11694	内存使用情况，怪现象！	windshome	69	2008-09-08 10:34
8263	Re:内存使用情况，怪现象！	JiafanZhou	65	2008-09-10 03:53
8526	Re:内存使用情况，怪现象！	windshome	157	2008-09-10 09:38
9196	Re:内存使用情况，怪现象！	JiafanZhou	2033	2008-09-10 19:31

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