On Nov 29, 2010, at 6:53 AM, Benson Margulies wrote:
> There's a recommendation on stack overflow to launch Eclipse with,
> amongst other things, the following options.
What's the URL?
> I'm having something of a
> bad day with my machine locking up (as in, the entire MacBook pro
> locks up),
Does it ever come out of this lock up? Is it just the CPU being at 100% all the time? Keep Activity Monitor running to see what happens. Shark traces could also help you.
> is it possible that some of this is a really bad idea?
Maybe. Let me explain what some of these options mean. Blindly adding options is not a good idea.
> -XX:CompileThreshold=5
You are telling hotspot to compile a java method to native after it has been invoked 5 times. This will cause a lot more methods to be compiled to native adding to memory pressure. Also, a small number means HotSpot may not have enough profiling information to generate the most optimized native code.
> -XX:MaxGCPauseMillis=10
So you're trying to hint to the garbage collector that it should try to limit application pause times to 10ms. That's awfully low. I am not sure what impact this would have. Try increasing this to 2000 or getting rid of this altogether to see what happens.
> -XX:MaxHeapFreeRatio=70
That's the default value so there's no point in passing this.
> -XX:+CMSIncrementalPacing
Set to true by default so again, no need to pass it.
> -XX:+UnlockExperimentalVMOptions
You need this simply for using the G1 GC.
> -XX:+UseG1GC
You're using the new G1 garbage collector. It's a new garbage collector written by Oracle. Use at your own risk. I am not sure how stable this is at the moment.
> -XX:+UseFastAccessorMethods
This is true by default so there's no point in adding it.
Fyi, there are some new flags available for help/diagnosis with VM options.
-XX:+PrintFlagsInitial
This will dump out all the default flag settings before HotSpot processes the passed in flags or does its own ergonomics tweaking.
-XX:+PrintFlagsFinal
This will print the value of the flags after HotSpot is done with processing.
-XX:+PrintCommandLineFlags
Prints the flags passed on command line or set by GC ergonomics.
There's a lot of output here but might give you some insights into the flag values. Documentation on some of these flags can be found at
http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.htmlhttp://developer.apple.com/library/mac/#documentation/Java/Reference/Java_VMOptionsRef/Articles/JavaVirtualMachineOptions.html
There's also
http://www.md.pp.ru/~eu/jdk6options.htmlhttp://blog.headius.com/2009/01/my-favorite-hotspot-jvm-flags.html
Pratik _______________________________________________
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