RFR (S): 8136854: G1 ConcurrentG1RefineThread::stop delays JVM shutdown for >150ms

[Thomas Schatzl]

Hi,

On Wed, 2016-01-27 at 09:37 -0500, Tom Benson wrote:
> Hi,
> Was the change tried on a small system to see if startup is actually 
> slowed down there, by the much tighter loop consuming CPU?  I guess 
> one possible answer is "we don't care that much about systems that 
> small for G1. " 

I did not try that, mainly because any delay using sleep() will very
likely be enough to move the thread off a cpu.

The actual code that is tested inside the polling loop is extremely
little, so even with an extremely slow cpu (say, around 1Ghz) the delay
should be much larger than the cpu time spent on checking the two
conditions.

> But Derek suggested an increasing delay scheme in the CR,
> which I don't think would be much more difficult than the current 
> change, and could address that.

I will do some tests to see if different delays make a significant
difference in CPU usage on some "slow" machine for a "Hello World"
style program.

Thanks,
  Thomas