RFR: 8204287: Phase timings not updated correctly after JDK-6672778

[Kim Barrett]

> On Jun 5, 2018, at 7:41 AM, Stefan Johansson <stefan.johansson at oracle.com> wrote:
> 
> Hi,
> 
> Please review this fix to do correct timings in G1.
> 
> Issue: https://bugs.openjdk.java.net/browse/JDK-8204287
> Webrev: http://cr.openjdk.java.net/~sjohanss/8204287/00/
> 
> Summary:
> When the partial trimming was introduced a while back the timing code in G1 became a bit more complicated. In one of the timer helpers a member structure is used before it is destructed and updated. This leads to the times being accounted to the wrong phases and there for the G1 ergonomics doing some less than optimal decisions.
> 
> Testing:
> * Local testing with jtreg
> * Mach5 testing tier 1-3 looks good
> * Sanity performance testing is running
> 
> Thanks,
> Stefan

Looks good.