RFR(s): 8234086: VM operation can be simplified

[Robbin Ehn]

Hi,

Here is v3:

Full:
http://cr.openjdk.java.net/~rehn/8234086/v3/full/webrev/
Inc:
http://cr.openjdk.java.net/~rehn/8234086/v3/inc/webrev/

Tested t1-3

Thanks, Robbin

On 2019-11-19 12:05, Robbin Ehn wrote:
> Hi all, please review.
> 
> CMS was the last real user of the more advantage features of VM operation.
> VM operation can be simplified to always be an stack object and thus either be
> of safepoint or no safepoint type.
> 
> VM_EnableBiasedLocking is executed once by watcher thread, if needed (default 
> not used). Making it synchrone doesn't matter.
> VM_ThreadStop is executed by a JavaThread, that thread should stop for the 
> safepoint anyways, no real point in not stopping direct.
> VM_ScavengeMonitors is only used to trigger a safepoint cleanup, the VM op is 
> not needed. Arguably this thread should actually stop here, since we are about 
> to safepoint.
> 
> There is also a small cleanup in vmThread.cpp where an unused method is removed.
> And the extra safepoint is removed:
> "// We want to make sure that we get to a safepoint regularly"
> No we don't :)
> 
> Issue:
> https://bugs.openjdk.java.net/browse/JDK-8234086
> Change-set:
> http://cr.openjdk.java.net/~rehn/8234086/v1/webrev/index.html
> 
> Tested scavenge manually, passes t1-2.
> 
> Thanks, Robbin