RFR: 8298377: JfrVframeStream causes deadlocks in ZGC

[Stefan Karlsson]

On Mon, 12 Dec 2022 13:15:24 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

> How important is the stack trace information for the ZPageAllocation event?

I don't know. I don't have any experience with looking at JFR Events with Loom stacks.

> What is it used for, i.e. does it give the user any information to change their code?

It's used as a way to see where the application spends a long time (> 1ms) in allocations, which is a cause for latency problems. Some reasons for long allocations: lock contention, over-provisioned machine, large object allocations, not using -Xms == -Xms + AlwaysPreTouch, etc.

> Is it used for ZGC devs to do what exactly? 

To look for scalability issues in the JVM. For those use-cases I have not really cared about the stack traces.

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PR: https://git.openjdk.org/jdk/pull/11586