RFR(S): 8232081: Try to link all classes during dynamic CDS dump
calvin.cheung at oracle.com
Fri Feb 28 00:48:32 UTC 2020
Hi David, Ioi,
Thanks for your review and suggestions.
On 2/26/20 9:46 PM, Ioi Lam wrote:
> On 2/26/20 7:50 PM, David Holmes wrote:
>> Hi Calvin,
>> Adding core-libs-dev as you are messing with their code :)
>> On 27/02/2020 1:19 pm, Calvin Cheung wrote:
>>> JBS: https://bugs.openjdk.java.net/browse/JDK-8232081
>>> webrev: http://cr.openjdk.java.net/~ccheung/jdk15/8232081/webrev.00/
>>> The proposed changeset for this RFE adds a JVM_LinkClassesForCDS()
>>> function to be called from java/lang/Shutdown to notify the JVM to
>>> link the classes loaded by the builtin class loaders. The
>> This would be much less disruptive if this was handled purely on the
>> VM side once we have started shutdown. No need to make any changes to
>> the Java side then, nor jvm.cpp.
> Hi David,
> To link the classes, we need to be able to run Java code -- when
> linking a class X loaded by the app loader, X will be verified. During
> verification of X, we may need to load additional classes from the app
> loader, which executes Java code during its class loading operations.
> We also need to handle all the exit conditions. As far as I can tell,
> an app can exit the JVM in two ways:
> (1) Explicitly calling System.exit(). This will call
> java.lang.Shutdown.exit() which does this:
> beforeHalt(); // native
> (2) When all non-daemon threads have died (e.g., falling out of the
> bottom of HelloWorld.main()). There's no explicit call to
> System.exit(), but the JVM will proactively call
> java.lang.Shutdown.shutdown() inside JavaThread::invoke_shutdown_hooks()
> If we want to avoid modifying the Java code, I think we can intercept
> JVM_BeforeHalt() and JavaThread::invoke_shutdown_hooks(). This way we
> should be able to handle all the classes (except those that are loaded
> inside Shutdown.runHooks).
I've implemented the above. No changes to the Java side.
I also updated the test to test the shutdown hook and System.exit()
All appcds tests passed on my linux host. I'll run more tests using mach5.
> What do you think?
> - Ioi
>>> MetaspaceShared::link_and_cleanup_shared_classes() has been modified
>>> to handle both static and dynamic CDS dump. For dynamic CDS dump,
>>> only classes loaded by the builtin class loaders will be linked.
>>> Local performance testing using javac on HelloWorld.java shows an
>>> improvement of >5%.
>>> Passed tier1 - 4 tests.
More information about the core-libs-dev