On Tue, 20 Dec 2022 02:04:01 GMT, Chris Plummer <cjplum...@openjdk.org> wrote:
> There are a few nsk debugger tests that pin multiple virtual threads to > carrier threads when synchronizing. Sometime the default number of carrier > threads (which equals the number of CPUs) is not enough, and the test > deadlocks because virtual threads start to wait forever for an available > carrier thread. This PR fixes this problem by using the > `jdk.virtualThreadScheduler.parallelism` property to change the default > number of carrier threads. I believe the largest number of carrier threads > any test needs is 11, so I chose 15 just to be safe. > > I had initially tried to fix each individual test by using the test support > in `VThreadRunner.setParallism()`. The advantage of this was limiting the > scope of the change to just a few tests, and also being able to specify the > exact number of needed carrier threads. The disadvantage was having to make > quite a few changes to quite a few tests, plus I had one troublesome test > that was still failing, I believe because I didn't fully understand how many > carrier threads it needed. Just giving every test 15 carrier threads in the > end was a lot easier. This sounds like a bug with the underlying executor. If the VT's pin their carrier threads then the executor should increase its parallelism level automatically to compensate for that. ------------- PR: https://git.openjdk.org/jdk/pull/11735
