> Hi all,
> 
> This PR refactors the newly added GC CPU time code from 
> [JDK-8359110](https://bugs.openjdk.org/browse/JDK-8359110).
> 
> As a stepping-stone to enable consolidation of CPU time tracking in e.g. 
> hsperf counters and GCTraceCPUTime and to have a unified interface for 
> tracking CPU time of various components in Hotspot this code can be 
> refactored. This PR introduces a new interface to retrieve CPU time for 
> various Hotspot components and it currently supports:
> 
> CPUTimeUsage::GC::total() // the sum of gc_threads(), vm_thread(), 
> stringdedup()
> 
> CPUTimeUsage::GC::gc_threads()
> CPUTimeUsage::GC::vm_thread()
> CPUTimeUsage::GC::stringdedup()
> 
> CPUTimeUsage::Runtime::vm_thread()
> 
> 
> I moved `CPUTimeUsage` to `src/hotspot/share/services` since it seemed 
> fitting as it housed similar performance tracking code like `RuntimeService`, 
> as this is no longer a class that is only specific to GC.
> 
> I also made a minor improvement in the CPU time logging during exit. Since 
> `CPUTimeUsage` supports more components than just GC I changed the logging 
> flag to from `gc,cpu` to `cpu` and created a detailed table:
> 
> 
> [71.425s][info][cpu   ] === CPU time Statistics 
> =============================================================
> [71.425s][info][cpu   ]                                                       
>                       CPUs
> [71.425s][info][cpu   ]                                                       
>          s       %  utilized
> [71.425s][info][cpu   ]    Process
> [71.425s][info][cpu   ]      Total                                            
>  1616.3627  100.00      22.6
> [71.425s][info][cpu   ]      VM Thread                                        
>     5.2992    0.33       0.1
> [71.425s][info][cpu   ]      Garbage Collection                               
>    83.7322    5.18       1.2
> [71.425s][info][cpu   ]        GC Threads                                     
>    82.7671    5.12       1.2
> [71.425s][info][cpu   ]        VM Thread                                      
>     0.9651    0.06       0.0
> [71.425s][info][cpu   ] 
> =====================================================================================
> 
> 
> Additionally, if CPU time retrieval fails it should not be the caller's 
> responsibility to log warnings as this would bloat the code unnecessarily. 
> I've noticed that `os` does log a warning for some methods if they fail so I 
> continued on this path.

Jonas Norlinder has updated the pull request incrementally with two additional 
commits since the last revision:

 - Minor improvements and fixes per @kstefanj suggestions
 - use percent_of from globalDefinitions.hpp

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/26621/files
  - new: https://git.openjdk.org/jdk/pull/26621/files/143fcacb..ddab1f0b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26621&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26621&range=04-05

  Stats: 118 lines in 4 files changed: 60 ins; 57 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/26621.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26621/head:pull/26621

PR: https://git.openjdk.org/jdk/pull/26621

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