RFR: 5641: Rule that looks at G1 MMU Information

[Henrik Dafgård]

On Fri, 26 May 2023 20:37:46 GMT, Alex Macdonald <aptmac at openjdk.org> wrote:

> This PR addresses JMC-5641 [[0]](https://bugs.openjdk.org/browse/JMC-5641), in which it would be nice to have a rule that looks at g1mmu information. Specifically, the issue makes note that this rule should compare gcTime of pauses and check if the pause time is over the target.
> 
> Example result when okay:
> ![g1mmu_okay](https://github.com/openjdk/jmc/assets/10425301/7b371027-d992-4d70-84fe-f8ad9ffb4088)
> 
> Example result when warning:
> ![g1mmu_warning](https://github.com/openjdk/jmc/assets/10425301/15803bc4-2d4f-4e53-9944-c97347564e39)
> 
> [0] https://bugs.openjdk.org/browse/JMC-5641

core/org.openjdk.jmc.flightrecorder.rules.jdk/src/main/java/org/openjdk/jmc/flightrecorder/rules/jdk/memory/GcPauseTargetRule.java line 120:

> 118: 							}
> 119: 						}
> 120: 					}

I'd prefer that we use a filter on the g1mmuItems that applies a comparison filter. E.g. ItemFilters.buildComparisonFilter(Kind.MORE, JdkAttributes.GC_TIME, pauseTarget) and then count the events in the resulting IItemCollection using an aggregator.

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PR Review Comment: https://git.openjdk.org/jmc/pull/488#discussion_r1221954243