频繁满GC，空堆 [英] Frequent full GC with empty heap

问题描述

我有一个GC日志文件，当堆空时（每30分钟一次，然后是20,10,5每分钟几次事件）显示频繁的完整GC。不过，在某些时候，我可以看到堆使用的突然增加（我想象在用户开始连接到我的应用程序的那一刻），并且完整的GC事件开始发生得不那么频繁。
我想不出为什么会发生这种情况。

我使用的是Oracle Vm 1.6，我的启动脚本是：

  java -XX：+ HeapDumpOnOutOfMemoryError \ 
 -Xmx7500m \ 
 -XX：HeapDumpPath = .. / logs \ 
 -verbose：gc \ 
 -XX ：+ PrintGCDetails \ 
 -XX：+ PrintGCTimeStamps \ 
 -Xloggc：/app/diffusion/Logs/gc.log \ 
 -Dcom.sun.management.jmxremote \ 
 -Dcom.sun.management.jmxremote.ssl = false \ 
 -Dcom.sun.management.jmxremote.authenticate = false \ 
 -Dcom.sun.management.jmxremote.port = 2000 \ 
 -cp ../lib/diffusion.jar:../etc:../data com.pushtechnology.diffusion.Diffusion $ 1 
  

解决方案

尝试禁用显式GC，看看它是否有帮助： -XX：+ DisableExplicitGC 。 然后，您可以收集几个线程转储，以确认应用程序中没有真正运行的应用程序堆是空的。

I've got a GC log file that shows frequent full GC when the heap is empty (every 30 mins initially, then 20, 10, 5 up to few events a minute. At some point, though, I can see a sudden increase in the heap usage (I'd imagine at the moment when users start connecting to my application) and full GC events start to take place less freqently. I can't think of a reason why this may happen.

I'm using Oracle Vm 1.6, and my startup script is:

java -XX:+HeapDumpOnOutOfMemoryError \
     -Xmx7500m \
     -XX:HeapDumpPath=../logs \
     -verbose:gc \
     -XX:+PrintGCDetails \
     -XX:+PrintGCTimeStamps \
     -Xloggc:/app/diffusion/Logs/gc.log \
     -Dcom.sun.management.jmxremote \
     -Dcom.sun.management.jmxremote.ssl=false \
     -Dcom.sun.management.jmxremote.authenticate=false \
     -Dcom.sun.management.jmxremote.port=2000 \
     -cp ../lib/diffusion.jar:../etc:../data com.pushtechnology.diffusion.Diffusion $1

解决方案

Try disabling explicit GC, see if it helps : -XX:+DisableExplicitGC.

Then, you could collect a few thread dumps to confirm that there is nothing really running in the app when the heap is empty.

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