The compatible lifecycle `ThreadStart/ThreadEnd` events were added in JDK 19 to support legacy virtual thread unaware JVMTI agents which do not enable the can_support_virtual_threads capability. When this capability is enabled then the `VirtualThreadStart/VirtualThreadEnd` instead of the `ThreadStart/ThreadEnd` events are generated for virtual threads and can be managed (enabled/disabled) separately. If the the `can_support_virtual_threads` capability is disabled then the `ThreadStart/ThreadEnd` events are generated for virtual threads. This enhancement is to get rid of the compatible lifecycle `ThreadStart/ThreadEnd` events. Motivation: Performance overhead from compatible lifecycle events can be significant when a lot of virtual threads are created.
Also, there is an experimental VM flag `PostVirtualThreadCompatibleLifecycleEvents` (enabled by default). If it is turned on then the default compatible lifecycle `ThreadStart/ThreadEnd` events for virtual threads are generated. This VM flag has to be removed now. Testing: The mach5 tiers 1-6 were submitted and passed. ------------- Commit messages: - 8307399: get rid of compatibility ThreadStart/ThreadEnd events for virtual threads Changes: https://git.openjdk.org/jdk/pull/13874/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13874&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8307399 Stats: 70 lines in 6 files changed: 18 ins; 29 del; 23 mod Patch: https://git.openjdk.org/jdk/pull/13874.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/13874/head:pull/13874 PR: https://git.openjdk.org/jdk/pull/13874
