Integrated: 8364638: Refactor and make accumulated GC CPU time code generic

[Jonas Norlinder]

On Mon, 4 Aug 2025 13:59:43 GMT, Jonas Norlinder <duke at openjdk.org> wrote:

> 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()
> 
> 
> 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   ]      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   ] =====================================================================================

This pull request has now been integrated.

Changeset: fb651fd6
Author:    Jonas Norlinder <jonas.norlinder at oracle.com>
Committer: Albert Mingkun Yang <ayang at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/fb651fd6d246e69b42363e050eb8d96afb633eed
Stats:     281 lines in 11 files changed: 202 ins; 76 del; 3 mod

8364638: Refactor and make accumulated GC CPU time code generic

Reviewed-by: ayang, sjohanss

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

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