[jdk26u] Integrated: 8373625: CPUTimeCounters creates a total counter for unsupported GCs

[jyma22]

On Mon, 22 Dec 2025 21:23:15 GMT, jyma22 <duke at openjdk.org> wrote:

> `CPUTimeCounters` unconditionally creates `CPUTimeGroups::CPUTimeType::gc_total`. Since only Parallel and G1 are supported by this framework/class, this leads to publishing a counter that always resolves to 0. This may be contradictory for an end-user especially so as we now support logging GC CPU time for any GC inside Hotspot. For an example using `-XX:+UseZGC -Xlog:cpu` we get
> 
> [7.907s][info][cpu] === CPU time Statistics =============================================================
> [7.907s][info][cpu]                                                                             CPUs
> [7.907s][info][cpu]                                                                s       %  utilized
> [7.907s][info][cpu]    Process
> [7.907s][info][cpu]      Total                                              186.9562  100.00      23.6
> [7.907s][info][cpu]      Garbage Collection                                   0.6700    0.36       0.1
> [7.907s][info][cpu]        GC Threads                                         0.6692    0.36       0.1
> [7.907s][info][cpu]        VM Thread                                          0.0008    0.00       0.0
> [7.907s][info][cpu] =====================================================================================
> 
> But `jcmd $(pgrep -n java) PerfCounter.print | grep -E "sun.threads.total_gc_cpu_time"` prints: `sun.threads.total_gc_cpu_time=0`.
> 
> Testing: passed tier1-4

This pull request has now been integrated.

Changeset: 4d138120
Author:    Jonas Norlinder <jnorlinder at openjdk.org>
Committer: Paul Hohensee <phh at openjdk.org>
URL:       https://git.openjdk.org/jdk26u/commit/4d1381209b94825395102efe7036b9b25ef369f5
Stats:     4 lines in 1 file changed: 3 ins; 0 del; 1 mod

8373625: CPUTimeCounters creates a total counter for unsupported GCs

Backport-of: 30be94086aad42b99a15a05fe5115f552e8efb8b

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PR: https://git.openjdk.org/jdk26u/pull/5