Small question about JDK-8253064 and ObjectMonitor allocation

Thomas Stüfe thomas.stuefe at gmail.com
Fri Jan 28 08:03:34 UTC 2022


Hi,

I have a small question about a detail of JDK-8253064.

IIUC, before this patch, the VM kept thread-local freelists of
pre-allocated ObjectMonitors to reduce allocation contention. Now we just
malloc monitors right away.

I looked through the issue and the associated PR, but could find no
information on why this was done. Dan describes what he did very well:
https://github.com/openjdk/jdk/pull/642#issuecomment-720753946, but not
why.

I assume that the complexity and memory overhead of the free lists was not
worth it? That you found that malloc() is on our platforms "uncontented"
enough?

Thank you,

Thomas


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