RFR: 8300811: jdb ThreadStartRequest and ThreadDeathRequest should use SUSPEND_NONE instead of SUSPEND_ALL

Thu Feb 2 17:45:34 UTC 2023

On Mon, 23 Jan 2023 21:02:51 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

> jdb creates a ThreadStartRequest and ThreadDeathRequest so it can track all created threads. It creates them with the SUSPEND_ALL policy. This is unnecessary since jdb always immediately resumes all threads after doing the thread bookkeeping. There is no interaction with the jdb user like there would be with something like a Breakpoint event, and therefore no reason to suspend.
> 
> I was debugging an app that does nothing except create threads and allow them to quickly exit. Changing the policy to SUSPEND_NONE sped up the execution of the app by about 100x (that's 100 times faster, not 100%)

Also, I think this fix is going to do a great job of "shaking the trees" and will
reveal some tests that were passing by accident. I'm looking forward to next
week when I roll from JDK20 Stress Kit testing to JDK21 Stress Kit testing!

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PR: https://git.openjdk.org/jdk/pull/12152