New Early Access builds
Alan.Bateman at oracle.com
Sat Jan 16 08:34:02 UTC 2021
We've published new builds on the Project Loom Early Access download
page . The new builds are based on jdk-17+5 (JDK 17 build 5) so we
are up to date with the main line. The "Getting started" page  is up
There are a few more stability fixes in this build, our testing has been
with G1 and ZGC.
As I mentioned in a previous mail, the debugger support has been work in
progress. The implementation of JVM TI (the underlying tools interface)
has been significantly updated since the last build. It's enough to get
jshell working again. There are still a few issues with some of the low
level events around scheduling points and we need to resolve those
issues before the IDE debuggers will step correctly.
We've started to explore serviceability/diagnosability features. JFR has
support for virtual threads for some time, it can record socket I/O
events on virtual threads that exceed some threshold for example. There
is also rudimentary support for thread dumps in this build in the form
of a new jcmd command and a new JDK-specific ThreadMXBean operation.
Use `jcmd <pid> JavaThread.dump -format=json` to get a thread dump in
JSON format. For now, the thread dump will only include the stack trace
of virtual threads when the new thread executors are used, and only when
they are used in a structured way. The JSON object has enough to allow
tools to reconstitute the structure, de-duplicate stack traces, and
other interesting things. We're re-evaulate all this at some point but
for now, it's something simple that does not require a stop-the-world
operation to find the virtual threads in the heap.
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