RFR: bot: add performance metrics for work items

[Erik Joelsson]

On Wed, 26 May 2021 13:51:02 GMT, Erik Helin <ehelin at openjdk.org> wrote:

> Hi all,
> 
> please review this patch that adds runtime performance metrics for work items. I have added three new gauges:
> 
> - `skara_runner_cpu_time`
> - `skara_runner_user_time`
> - `skara_runner_allocated_bytes`
> 
> All three are per work item and make use of the `ThreadMXBean` to set the gauges. We can use the methods in `ThreadMXBean` because the `Runnable` that is running on a thread in the thread pool cannot be preempted or moved to another thread, i.e. it will have the same "carrier" thread for its whole execution.
> 
> Testing:
> - [x] Manual testing on Linux x64 using the mirror bot
> 
> Thanks,
> Erik

This looks pretty cool!

Marked as reviewed by erikj (Lead).

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PR: https://git.openjdk.java.net/skara/pull/1171