java.lang.management, com.sun.management API and JVM TI only report Java
threads. The internal GC threads are not Java threads and are
filtered. There is no supported API to get the safepoint time and
GC/compiler thread CPU time.
I also think that the internal thread CPU time/usage are useful to
monitor. It's worth considering exposing those statistics through
com.sun.management API and/or via JFR.
Mandy
On 9/27/21 9:30 PM, Dylan Wragge wrote:
Hey serviceability devs,
I'm currently looking to migrate our company's codebases to JDK 17 and
am running into an issue where sun.management.HotspotThreadMBean and
HotspotRuntimeMBean are no longer accessible from client code. We have
a few internal metrics that use this MBean in order to provide
counters on safepoint time and internal thread (GC/Compiler/etc) CPU
time/usage.
Safepoint time is nicely exposed as JFR events, which can be consumed
easily with the streaming JFR API. Internal thread CPU time is proving
difficult to access however. Other APIs I've tried seem to hide the
existence of the GC threads altogether (which we are most interested
in). So far I've tried JFR's ThreadCPUTime event and JVMTI's
GetAllThreads/GetThreadInfo, both of which don't seem to include any
of the internal GC threads. The MBean also does not seem to be
registered by default, so seems totally inaccessible. Although even if
it were, JEP 396 would stop me accessing any of its methods.
Is there a supported method in JDK 17 to get this information? To me
this seems like a reasonable use case. In the past, we've found these
metrics extremely useful when evaluating and tuning new GCs. I managed
to get something working by scraping /proc but it feels like there
should be a better (and more portable) way.
- Dylan
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