Restrictions for lock coarsening?

[Tom Rodriguez]

The delay is actually a timeout for a periodic one-shot task so I  
don't think it triggers until the initial jvm bootstrap finishes.  It  
before main runs though so it should get everything interesting.  A  
absolutely accurate comparison would require modifying the VM.

tom

On Jan 8, 2009, at 10:24 AM, Christian Thalinger wrote:

> On Thu, 2009-01-08 at 10:11 -0800, Tom Rodriguez wrote:
>> It was definitely done as a result of benchmarking and there were
>> definitely regressions.  I don't have any information about which
>> benchmarks showed problems though.  I think it was done early enough
>> that other changes and improvements to biased locking might have
>> helped.  Maybe that's just wishful thinking on my part.
>
> I try to have a look at it.  Does setting BiasedLockingStartupDelay=0
> use biased locking for all locks?  I'm not sure:
>
> $ gamma -XX:+TraceBiasedLocking -XX:BiasedLockingStartupDelay=0 x
> VM option '+TraceBiasedLocking'
> VM option 'BiasedLockingStartupDelay=0'
> Aligned thread 0x0000000000446418 to 0x0000000000446800
> Aligned thread 0x0000000000453fc8 to 0x0000000000454000
> Aligned thread 0x0000000000455d18 to 0x0000000000456000
> Aligned thread 0x0000000000597968 to 0x0000000000598000
> Aligned thread 0x000000000059d448 to 0x000000000059d800
> Aligned thread 0x000000000059f658 to 0x000000000059f800
> Aligned thread 0x00000000005d5688 to 0x00000000005d5800
> Aligned thread 0x00000000005d7f08 to 0x00000000005d8000
> Aligned thread 0x00000000005db198 to 0x00000000005db800
> Aligned thread 0x00000000005df558 to 0x00000000005df800
> Biased locking enabled
> Aligned thread 0x00000000005eb5a8 to 0x00000000005eb800
> Exception in thread "main" java.lang.NoClassDefFoundError: x
> Caused by: java.lang.ClassNotFoundException: x
> 	at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
> 	at java.security.AccessController.doPrivileged(Native Method)
> 	at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
> 	at java.lang.ClassLoader.loadClass(ClassLoader.java:323)
> 	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
> 	at java.lang.ClassLoader.loadClass(ClassLoader.java:268)
> 	at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:336)
>
> - Christian
>