RFR: 8157023: Integrate NMT with JFR [v2]

[Thomas Stuefe]

On Mon, 5 Dec 2022 10:16:56 GMT, Stefan Johansson <sjohanss at openjdk.org> wrote:

> > I did some tests and on my box probing 20k threads - if we get ThreadCritical right away - takes about 50-100ms.
> 
> Ok, so the summary is stalled that long because somebody is already in a `ThreadCritical` (like registering a new thread stack) or do you mean that the actual baseline (stack-walk) takes that long, so we potentially stall other caller of `ThreadCritical`?

I see both.

I have a test with 20k threads. On my machine time under ThreadCritical fluctuates between 30 and 70 ms (I measured debug before accidentally, this is for a release VM). When there is high thread activity (e.g. 20k threads joining), time until we get ThreadCritical can be up to 20 seconds.

-------------

PR: https://git.openjdk.org/jdk/pull/11449