8298099: [JVMCI] decouple libgraal from JVMCI module at runtime #11513

dougxc · 2022-12-05T13:16:25Z

Libgraal is compiled ahead of time and should not need any JVMCI Java code to be dynamically loaded at runtime. Prior to this PR, this is not the case due to:

Code to copy system properties from the HotSpot heap into the libgraal heap. This is in jdk.vm.ci.services.Services.initializeSavedProperties(byte[]) and jdk.vm.ci.services.Services.serializeSavedProperties(). This code should be moved to java.base/jdk.internal.vm.VMSupport.
Code to translate exceptions from the HotSpot heap into the libgraal heap and vice versa. This code should be moved from jdk.internal.vm.ci//jdk.vm.ci.hotspot.TranslatedException to java.base/jdk.internal.vm.VMSupport.

This PR makes the above changes. As a result, it's possible to build a JDK image that includes (and uses) libgraal but does not include jdk.internal.vm.ci or jdk.internal.vm.compiler. This both reduces footprint and better isolates the JVMCI and the Graal compiler as accessing these components from Java code is now impossible.

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Issue

JDK-8298099: [JVMCI] decouple libgraal from JVMCI module at runtime

Reviewers

Tom Rodriguez (@tkrodriguez - Reviewer) ⚠️ Review applies to bdbe7cf2

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk pull/11513/head:pull/11513
$ git checkout pull/11513

Update a local copy of the PR:
$ git checkout pull/11513
$ git pull https://git.openjdk.org/jdk pull/11513/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 11513

View PR using the GUI difftool:
$ git pr show -t 11513

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/11513.diff

bridgekeeper · 2022-12-05T13:17:22Z

👋 Welcome back dnsimon! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2022-12-05T13:21:37Z

@dougxc The following labels will be automatically applied to this pull request:

core-libs
hotspot

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

mlbridge · 2022-12-05T13:24:57Z

Webrevs

AlanBateman · 2022-12-05T13:32:38Z

src/hotspot/share/classfile/classLoader.cpp

 }

+// Returns true if jdk.internal.vm.ci is present on the file system.
+bool ClassLoader::has_jvmci_module() {


Would it be more useful to pass the module name so that the function tests if the module is is in the run-time image so that ClassLoader doesn't need to know the name "jdk.internal.vm.ci"?

Yes, good idea: 3e89d40253b70251f9a2facce4b1d8d69701c045
I also fixed a bug due in the size computation of path. Ideally, I'd factor out and re-use the same code in ClassLoader::add_to_exploded_build_list. However, the latter uses a ResourceMark which is not available when calling is_module_resolvable early in VM startup before JavaThread is initialized.

dougxc · 2022-12-05T13:53:07Z

src/hotspot/share/classfile/classLoader.hpp

-  static bool has_jvmci_module();
+
+  // Determines if the `module_name` module is resolvable.
+  static bool is_module_resolvable(const char* module_name);


Is "resolvable" the right concept here? Or should it be something like "findable" instead?

Assuming --limit-modules isn't used, it is testing if the module is "observable".

I assume this function should therefore be named is_module_observable?

How about this:

// Determines if the named module is present in the // modules jimage file or in the exploded modules directory. static bool is_module_observable(const char* module_name);

That looks okay to me. I don't have any other comments on this part.

…ased variable length array

dholmes-ora

Sorry Doug not a full review (not familiar enough with code) but a few drive-by nits.

Thanks.

dholmes-ora · 2022-12-06T05:28:24Z

src/hotspot/share/jvmci/jvmci.cpp

+    if (thread != nullptr && thread->is_Java_thread()) {
      ResourceMark rm;
-      tty->print("JVMCITrace-%d[%s]:%*c", level, thread->name(), level, ' ');
+      JavaThreadState state = ((JavaThread*) thread)->thread_state();


Please use JavaThread::cast(thread)

I've made this change. Out of interest, I grep'ed through src/hotspot and found a few other instances of (JavaThread*) style casts. While most of these are probably older code, I'm wondering what the guidelines are in this area. I assume JavaThread::cast should be preferred always given the assertion checking it does?

Yes JavaThread::cast(t) is preferred. We did a lot of cleanup work ensuring we use JavaThread when always dealing with a JavaThread, and so reduce the places we need to cast. I'm a little surprised we still have some raw casts left as I thought we had cleaned them all up. I will check and file another cleanup RFE. Thanks.

dholmes-ora · 2022-12-06T05:31:17Z

src/hotspot/share/jvmci/jvmci.cpp

    Thread* thread = Thread::current_or_null_safe();
-    if (thread != nullptr) {
+    if (thread != nullptr && thread->is_Java_thread()) {
      ResourceMark rm;


You can pass thread to the rm constructor to save an internal lookup.

dholmes-ora · 2022-12-06T05:39:35Z

src/hotspot/share/jvmci/jvmci.cpp

+        // According to check_access_thread_state, it's unsafe to
+        // resolve the j.l.Thread object unless the thread is in
+        // one of the states above.
+        tty->print("JVMCITrace-%d[%s@" INTPTR_FORMAT "]:%*c", level, thread->type_name(), p2i(thread), level, ' ');


I think the current preferred style is to use PTR_FORMAT here.

dholmes-ora · 2022-12-06T05:49:09Z

src/java.base/share/classes/jdk/internal/vm/TranslatedException.java

@@ -1,10 +1,12 @@
 /*
- * Copyright (c) 2018, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.


If you just moved the file the original copyright year should remain - this is not new code.

dholmes-ora · 2022-12-06T05:57:40Z

src/hotspot/share/runtime/arguments.cpp

-    if (!create_numbered_module_property("jdk.module.addmods", "jdk.internal.vm.ci", addmods_count++)) {
-      return false;
+    if (ClassLoader::is_module_observable("jdk.internal.vm.ci")) {
+      if(!create_numbered_module_property("jdk.module.addmods", "jdk.internal.vm.ci", addmods_count++)) {


Nit: space after if please

AlanBateman · 2022-12-06T13:02:40Z

src/java.base/share/classes/jdk/internal/vm/TranslatedException.java

+ * Support for translating exceptions between the HotSpot heap and libjvmci heap.
 */
 @SuppressWarnings("serial")
 final class TranslatedException extends Exception {


Would it be possible to re-format this to avoid the wildly long (150+) lines? This seems to be moving jdk.vm.ci.hotspot.TranslatedException and hard to see what is going on.

Is there some tool support for formatting Java source code to meet OpenJDK coding guidelines? Rather unfortunate that one has to do this manually and reviewers have to spend time manually checking it.

There isn't globally agreed code conventions. The cleanup in the latest version looks okay.

AlanBateman · 2022-12-06T13:05:07Z

src/java.base/share/classes/jdk/internal/vm/VMSupport.java

+     *               only contains String keys and values.
     */
-    private static byte[] serializePropertiesToByteArray(Properties p) throws IOException {
+    private static byte[] serializePropertiesToByteArray(Properties p, boolean filter) throws IOException {


I think we need more context as to why there are non-String system properties in use here.

This parameter exists to allow a caller to pass in a Properties object that is guaranteed to have only String keys and so does not need the extra filtering done in this method. I'll refactor the code to make it clearer.

Hopefully this makes it clearer: 5c61079

Thanks. I initially assumed it was done to support non-String key/values but it's actually an optimization because the save properties are always Strings.

AlanBateman · 2022-12-06T13:05:46Z

src/java.base/share/classes/jdk/internal/vm/VMSupport.java

+            props.put(e.getKey(), e.getValue());
+        }
+        if (props.get("oome") != null) {
+            throw new OutOfMemoryError("forced OOME");


I don't think code in java.base should be checking for a property named "oome". Is this for a test that sets this system property on the command line?

Sorry, that's debug code that I will remove.

Thanks, I couldn't see it set as a property anywhere so didn't know why it was there. I don't have any comments on this area.

openjdk · 2022-12-07T06:10:13Z

@dougxc This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8298099: [JVMCI] decouple libgraal from JVMCI module at runtime

Reviewed-by: never

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been no new commits pushed to the master branch. If another commit should be pushed before you perform the /integrate command, your PR will be automatically rebased. If you prefer to avoid any potential automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

AlanBateman · 2022-12-07T18:42:43Z

src/java.base/share/classes/jdk/internal/vm/TranslatedException.java

    private static Throwable create(String className, String message, Throwable cause) {
        // Try create with reflection first.
        try {
            Class<?> cls = Class.forName(className);


A question about the Class.forName usage here. Class.forName uses the defining class loader of the current class so I'm wondering if the exceptions to be decoded are always of a type defined to the boot loader? jdk.internal.vm.ci is defined to the boot loader so this code hasn't really changed, it's just "new" to java.base in this PR.

The exceptions can be of any type and defined by any loader. In the case that Class.forName fails, the name of the original exception type is shown as part of TranslationException.toString(). Combined with the stack trace, this has always been sufficient to understand the origin of an exception thrown on a HotSpot/libjvmci mixed stack.

dougxc · 2022-12-07T22:10:04Z

/integrate

openjdk · 2022-12-07T22:11:27Z

Going to push as commit 8b69a2e.
Since your change was applied there have been 2 commits pushed to the master branch:

8a9911e: 8295803: Console should be usable in jshell and other environments
5d4c71c: 8281236: (D)TLS key exchange named groups

Your commit was automatically rebased without conflicts.

openjdk · 2022-12-07T22:11:44Z

@dougxc Pushed as commit 8b69a2e.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

dholmes-ora · 2022-12-08T02:42:10Z

@dougxc Two reviews are needed for all non-trivial hotspot changes, and this also warranted a review from core-libs! Your discussions with Alan still seemed to be in-progress.

dougxc · 2022-12-08T07:51:00Z

Sorry I checked with Alan over Slack who said to go ahead with merging.

AlanBateman · 2022-12-08T07:53:53Z

Sorry I checked with Alan over Slack who said to go ahead with merging.

Yeah, I was busy at the time and didn't get a chance to say that I didn't have any more comments/issues.

dougxc added 4 commits December 5, 2022 12:39

only resolve jdk.internal.vm.ci if it is present on the file system

a31ef72

move JVMCI system properties support into VMSupport

4493336

move JVMCITraceMark blocks within scope of C2V_BLOCK (GR-40773)

de558a4

move JVMCI exception translation support into VMSupport

b91f31f

openjdk bot added the rfr Pull request is ready for review label Dec 5, 2022

openjdk bot added hotspot hotspot-dev@openjdk.org core-libs core-libs-dev@openjdk.org labels Dec 5, 2022

AlanBateman reviewed Dec 5, 2022

View reviewed changes

generalized ClassLoader::has_jvmci_module to is_module_resolvable

3e89d40

dougxc commented Dec 5, 2022

View reviewed changes

dougxc added 2 commits December 5, 2022 16:06

share code to create the exploded path for a module and avoid stack-b…

7b147f2

…ased variable length array

renamed is_module_resolvable to is_module_observable

29e100b

dholmes-ora suggested changes Dec 6, 2022

View reviewed changes

dougxc added 2 commits December 6, 2022 10:27

removed hard-coded module name [skip ci]

a2467fc

incorporate review feedback [skip ci]

342d5e3

AlanBateman reviewed Dec 6, 2022

View reviewed changes

dougxc added 4 commits December 6, 2022 16:30

remove debug code [skip ci]

1511e67

clarify Properties filtering [skip ci]

5c61079

removed debug code [skip ci]

a5935b9

formatting to avoid very long lines [skip ci]

bdbe7cf

tkrodriguez approved these changes Dec 7, 2022

View reviewed changes

openjdk bot added the ready Pull request is ready to be integrated label Dec 7, 2022

AlanBateman reviewed Dec 7, 2022

View reviewed changes

Merge remote-tracking branch 'openjdk-jdk/master' into JDK-8298099

f5219b2

openjdk bot added the integrated Pull request has been integrated label Dec 7, 2022

openjdk bot closed this Dec 7, 2022

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Dec 7, 2022

dougxc deleted the JDK-8298099 branch May 23, 2023 07:51

8298099: [JVMCI] decouple libgraal from JVMCI module at runtime #11513

8298099: [JVMCI] decouple libgraal from JVMCI module at runtime #11513

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