On Tue, 20 Dec 2022 05:21:21 GMT, David Holmes <dhol...@openjdk.org> wrote:
>> Chris Plummer has updated the pull request incrementally with one additional >> commit since the last revision: >> >> Better comments. > > The JEP defines pinning as expected: >> There are two scenarios in which a virtual thread cannot be unmounted during >> blocking operations because it is pinned to its carrier: >> >> When it executes code inside a synchronized block or method, or >> When it executes a native method or a [foreign >> function](https://openjdk.java.net/jeps/424). >> >> Pinning does not make an application incorrect, but it might hinder its >> scalability. If a virtual thread performs a blocking operation such as I/O >> or BlockingQueue.take() while it is pinned, then its carrier and the >> underlying OS thread are blocked for the duration of the operation. Frequent >> pinning for long durations can harm the scalability of an application by >> capturing carriers. > > But then also says: >> The scheduler does not compensate for pinning by expanding its parallelism. > > which contradicts what you quoted from Alan above - though I prefer that > behaviour as the JEP's behaviour seems a design flaw to me. @dholmes-ora I initially took the approach of making sure each test that was ever running short of carrier threads explicitly requested the minimum it needed. It resulted in quite a few changes, and I still had one test that was occasionally failing. Possibly I just came up one short in the carrier thread calculation. I abandoned it for this PR because it's much simpler. Here's a PR I just created for those changes in case you want to have a look at what was involved: #11762. ------------- PR: https://git.openjdk.org/jdk/pull/11735
