如何调整jvm崩溃而不是英雄GC直到100％的CPU利用率？

Question

We have a JVM process that infrequently pegs the CPU at 100%, with what appears to be (according to visualgc) a very nearly exhausted heap. Our supposition is that the process is heroically GC'ing causing a CPU spike, which is affecting the overall health of the entire system (consisting of other JVMs doing different things).

This process is not critical and can be restarted. Is there a way to tune the JVM via the command line which starts it to make it fall on its own sword rather than it keep GC'ing and causing the entire box to suffer?

Of note is that we are not getting OOMExceptions, so the heap isn't TOTALLY exhausted, but just barely not, we think.

Alternatively, something to give us some insight as to what in the JVM is actually using the CPU in the way that it is to confirm/deny our GC supposition?

Answer 1

We can get the statistics from

1):The option -XX:+PrintGCTimeStamps will add a time stamp at the start of each collection. This is useful to see how frequently garbage collections occur.

With the above option we can get rough estimation whether you supposition that the process is heroically GC'ing causing a CPU spike or not .

If your suppossition is right then start tunig your GC .

 Both parallel collector and Concurrent Collector will throw an OutOfMemoryError if too much time is being
 spent in garbage collection: if more than 98% of the total time is spent in garbage collection and 
less than 2% of the heap is recovered, an OutOfMemoryError will be thrown. the option X:-UseGCOverheadLimit 
 is enabled by default for both Parallel and concurrent collector . Check whether this option is disabled in
 your system .  

For more information about Gc tuning in JVM refer this and for vm debugging options check this

Answer 2

The parallel and concurrent collectors have an "overhead limit" that might do what you want:

if more than 98% of the total time is spent in garbage collection and less than 2% of the heap is recovered, an OutOfMemoryError will be thrown

See http://www.oracle.com/technetwork/java/javase/gc-tuning-6-140523.html for more information.

Answer 3

The best thing to do is to find out the memory leak and fix it.

A simple way to exit on high memory usage:

if(Runtime.getRuntime().totalMemory()>100*1024*1024)
    System.exit(0);

Answer 4

Try to look what processes are currently running in the JVM.

• with jstack you can make a thread dump (there are other ways to do that as well)
• with jvisualvm you could peek into the current state of the JVM (takes some resources)
• also turn on verbosegc (to prove your assumption that GC is frequent)

Answer 5

You need to find a way how to gather some statistic about GC work. Actually there are some methods to do this. I will not do copy-paste, just give you the link to similar question:

Can you get basic GC stats in Java?

I believe, you will think of how to analyze this statistic and decide when GC is constantly active.

Because this question contains some new idea of applying GC statistic, I don't think, that it is duplicate.