JDK-8283674 : Pad ObjectMonitor allocation size to cache line size
  • Type: Bug
  • Component: hotspot
  • Sub-Component: runtime
  • Affected Version: 19
  • Priority: P4
  • Status: Resolved
  • Resolution: Won't Fix
  • Submitted: 2022-03-25
  • Updated: 2022-06-24
  • Resolved: 2022-06-24
Related Reports
Relates :  
JDK-8253064 - monitor list simplifications and getting rid of TSM
Relates :  
JDK-8049737 - Contended Locking reorder and cache line bucket
Description
See discussion under [1].

Since the libc malloc allocator may place ObjectMonitor instances adjacent to each other, we should pad the size of ObjectMonitor to fill a whole cache line to prevent false sharing between adjacent OMs.

[1] https://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2022-March/054187.html
Comments
Has been controversial - see review at https://github.com/openjdk/jdk/pull/7955 - therefore I close this issue as wontfix.
24-06-2022
A pull request was submitted for review. URL: https://git.openjdk.java.net/jdk/pull/7955 Date: 2022-03-25 09:02:28 +0000
26-03-2022