Open Sir-Will opened 4 years ago
Will investigate and see what info OpenJ9 can provide via jstat -gc
?
As per [1], RI jstat -gc
displays statistics about the behavior of the garbage collected heap with following output columns:
S0C: Current survivor space 0 capacity (KB).
S1C: Current survivor space 1 capacity (KB)
S0U: Survivor space 0 utilization (KB).
S1U: Survivor space 1 utilization (KB).
EC: Current eden space capacity (KB).
EU: Eden space utilization (KB).
OC: Current old space capacity (KB).
OU: Old space utilization (KB).
MC: Metaspace Committed Size (KB).
MU: Metaspace utilization (KB).
CCSC: Compressed class committed size (KB).
CCSU: Compressed class space used (KB).
YGC: Number of young generation garbage collection (GC) events.
YGCT: Young generation garbage collection time.
FGC: Number of full GC events.
FGCT: Full garbage collection time.
GCT: Total garbage collection time.
@dmitripivkine does OpenJ9 GC have similar statistic data available?
[1] https://docs.oracle.com/en/java/javase/14/docs/specs/man/jstat.html
Most of this information is around. Currently it can be found in GC verbose logs (per GC basis). Summary can be seen as report in GCMV (terminology can be different). The only part is not there is Metaspace and Class space information. These parts of information can be discovered in javacore
in NATIVEMEMINFO subcomponent dump routine
section
Ok, this is existing run-time utility required to be extended to report more data. The work required in GC part is review current stats info stored already and add/maintain new fields if necessary to be ready to report run-time. We should investigate which parts of native memory allocations should be included to report as Metadata space (something else except GC Metadata?) On VM/Tools side an utility should be updated to add GC related information to report @amicic FYI
Hi, I'm completely new to open source and would like to try this. How do I start and what should I do to solve this?
@ttorpy welcome to OpenJ9, a start point is openj9/tools/attach/diagnostics/tools/Jstat.java
OpenJ9 build instructions - https://github.com/eclipse-openj9/openj9/tree/master/doc/build-instructions
@ttorpy are you still working on this? Is there any way I can help if you still are?
@ttorpy same question bud
Hi, I'm sorry I am not working on this anymore. I think this was way above my skill level.
Hello,
It would be great if OpenJ9 had a command like hotspot has
jstat -gc
which allows retrieving information like heap usage and GC time of a specified process.For hotspot, I'm using munin plugins linked below to monitor the java processes, unfortunately I'm not able to find a way to do that with OpenJ9. https://github.com/munin-monitoring/contrib/tree/master/plugins/jvm