JDK-8221475 : Unnecessary safe point when using OldObject sample events with cutoff=0
  • Type: Bug
  • Component: hotspot
  • Sub-Component: jfr
  • Affected Version: 13,14
  • Priority: P4
  • Status: Closed
  • Resolution: Duplicate
  • Submitted: 2019-03-26
  • Updated: 2020-02-11
  • Resolved: 2019-09-02
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tbdResolved
Related Reports
Duplicate :  
JDK-8214542 - JFR: Old Object Sample event slow on a deep heap in debug builds
Description
When using the old object sample events, there is an unnecessary safe pointing vm operation (GC_HeapInspection) happening when the memory-leak-detection-cutoff=0.
Comments
Very nice! Thank you!
02-08-2019
Updating ILW based on the feedback: ILW = MLM = P4
11-07-2019
This is still a bit worrying. For someone wanting to do short recording every once in a while, but still have the oldobjectsample event enabled, there will be extra safe points. For some customers this may be enough to turn it off.
27-03-2019
RT Triage: This is a P5. We will not address this issue.
27-03-2019
ILW: LMM -> p5 I: Low - slight pause/performance drop L: M - it will always happen with this events and option W: M: do not use OldObjectSample
27-03-2019
Not saying it shouldn't be fixed, but it may be worth mentioning that the time in safepoint is really short. The JVM traverses a linked list and emits 50-100 events.It shouldn't take more than a few microseconds, even though bringing the JVM to a safepoint is more expensive, which happens all the time (deoptimizations, revokebias etc). The JVM doesn't iterate/inspect the heap if cutoff=0, so the name of the safepoint is misleading. Also, the OldObjectSample event is only emitted when a recording ends, not at every chunk rotation.
27-03-2019