JDK-8274178 : Occupancy value in logging and JFR event is inaccurate in G1IHOPControl
  • Type: Bug
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 9,10,11,12,13,14,15,16,17,23
  • Priority: P4
  • Status: Open
  • Resolution: Unresolved
  • Submitted: 2021-09-22
  • Updated: 2025-05-15
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JDK 26
26Unresolved
Related Reports
Relates :  
JDK-8143220 - Fix documentation of InitiatingHeapOccupancyPercent
Relates :  
JDK-8136677 - Adaptive sizing for IHOP in G1
Description
After JDK-8136677 and JDK-8143220, "occupancy" for G1 IHOP is now computed by this formula:

region_size * (num_old_regions + num_humongous_regions) + new_humonogous_alloc_bytes

However, in G1IHOPControl::print(), G1AdaptiveIHOPControl::print(), G1IHOPControl::send_trace_event() and G1AdaptiveIHOPControl::send_trace_event(), the occupancy value is G1CollectedHeap::heap()->used(), which includes used bytes in young regions and does not include wasted space in old regions.

I'll sponsor my colleague Jonathan Joo to fix this.
Comments
Thank you! The Oracle GC triage team tends to try to have our open bugs on the current or the next JDK release, so that we always have the bugs in sight for each release. So, I'm going to put Fix Version to 26 and we'll reevaluate check again the next release. (RFEs we tend to put as tbd)
15-05-2025
Apology for neglecting this issue. We are not actively working on this, but hopefully will pick up https://github.com/openjdk/jdk/pull/5762 again when I have time. I changed "Fix Version" to tbd.
15-05-2025
[~manc][~jjoo] Do you have any plans to continue this work? We're going over P4 Bugs in preparation to defer those that we'll not get to before the JDK 25 fork.
12-05-2025