8265602: -XX:DumpLoadedClassList should support custom loaders #4952

iklam · 2021-08-02T06:39:37Z

Some applications load a lot of classes using custom loaders. This PR improves the start-up performance of these apps when using a "static" CDS archive:

Here are performance numbers for the Eclipse IDE:

Static Archive Before: 7.31 sec (classlist does not include custom loader classes)
Static Archive After:  6.49 sec (classlist includes custom loader classes)
Dynamic Archive:       6.62 sec

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Issue

JDK-8265602: -XX:DumpLoadedClassList should support custom loaders

Reviewers

Calvin Cheung (@calvinccheung - Reviewer) ⚠️ Review applies to 04ae485
Yumin Qi (@yminqi - Reviewer) ⚠️ Review applies to 04ae485

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$ git checkout pull/4952

Update a local copy of the PR:
$ git checkout pull/4952
$ git pull https://git.openjdk.java.net/jdk pull/4952/head

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bridgekeeper · 2021-08-02T06:40:01Z

👋 Welcome back iklam! 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 · 2021-08-02T06:42:11Z

@iklam The following label will be automatically applied to this pull request:

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iklam · 2021-08-02T06:51:50Z

/label remove hotspot
/label add hotspot-runtime

openjdk · 2021-08-02T06:52:44Z

@iklam
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openjdk · 2021-08-02T06:54:13Z

@iklam
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mlbridge · 2021-08-02T07:02:54Z

Webrevs

calvinccheung · 2021-08-04T01:40:18Z

src/hotspot/share/cds/archiveUtils.cpp

@@ -330,23 +330,24 @@ void ReadClosure::do_region(u_char* start, size_t size) {
  }
 }

-fileStream* ClassListWriter::_classlist_file = NULL;
-
 void ArchiveUtils::log_to_classlist(BootstrapInfo* bootstrap_specifier, TRAPS) {
  if (ClassListWriter::is_enabled()) {
    if (SystemDictionaryShared::is_supported_invokedynamic(bootstrap_specifier)) {
      ResourceMark rm(THREAD);


Line 336 could be moved after line 338.

calvinccheung · 2021-08-04T01:41:02Z

src/hotspot/share/cds/classListWriter.cpp

+void ClassListWriter::write(const InstanceKlass* k, const ClassFileStream* cfs) {
+  assert(is_enabled(), "must be");


Should assert_locked() be added here?

This function doesn't need the lock, since it doesn't directly use ClassListWriter::_classlist_file or ClassListWriter::_id_table, which are protected by ClassListFile_lock. The lock will be taken a few lines down, in the ClassListWriter constructor.

Your comment reminded me to look for places that need the lock. As a result, I added assert_locked() to ClassListWriter::write_to_stream().

calvinccheung · 2021-08-04T01:42:12Z

src/hotspot/share/cds/classListWriter.hpp

+#else
+public:
+  static bool is_enabled() {
+    return false;
  }
 #endif


Please add // INCLUDE_CDS after endif.

calvinccheung · 2021-08-04T01:44:05Z

test/hotspot/jtreg/runtime/cds/appcds/customLoader/test-classes/CustomLoadee4WithLambda.java

+public class CustomLoadee4WithLambda {
+    public static void test() {
+        doit(() -> {
+                System.out.println("Hello inside a Lambda expression");
+            });
+    }


We have a similar class in dynamicArchive/test-classes/LambHello.java.
To avoid changes in existing tests, maybe you can just add a test() method there.

LambHello is in a separate directory and is used by several existing tests that require the function doTest(). If I add another test() function there it kind of looks odd. Also, I don't want to introduce inter-dependencies between too many tests. Since this class is small, I prefer to keep it separate.

calvinccheung

Looks good. Just a few minor comments.

yminqi

Looks good!
One concern is that this patch works for custom class in a plain jar file, but won't work with if the class loader has its own way to load class from more complicated location like "fat" jar, is it correct?

yminqi · 2021-08-04T15:15:28Z

test/hotspot/jtreg/runtime/cds/appcds/test-classes/DumpClassListApp.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.


Is this a new file?

Yes, it is a new file. In my first commit I included 2016 in the copyright by mistake, so I removed it in the second commit.

iklam · 2021-08-04T18:07:37Z

Looks good!
One concern is that this patch works for custom class in a plain jar file, but won't work with if the class loader has its own way to load class from more complicated location like "fat" jar, is it correct?

That's correct, I have filed JDK-8271598 (CDS classlist file should support uber JARs) to handle this issue.

openjdk · 2021-08-04T19:40:50Z

@iklam 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:

8265602: -XX:DumpLoadedClassList should support custom loaders

Reviewed-by: ccheung, minqi

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.

calvinccheung

Looks good.

iklam · 2021-08-06T05:57:20Z

Thanks @calvinccheung and @yminqi for the review.
/integrate

openjdk · 2021-08-06T05:58:55Z

Going to push as commit e7b6f48.
Since your change was applied there has been 1 commit pushed to the master branch:

ea02dad: 8272067: Initial nroff manpage generation for JDK 18

Your commit was automatically rebased without conflicts.

openjdk · 2021-08-06T05:59:09Z

@iklam Pushed as commit e7b6f48.

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

8265602: -XX:DumpLoadedClassList should support custom loaders

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openjdk bot added the hotspot hotspot-dev@openjdk.org label Aug 2, 2021

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iklam marked this pull request as ready for review August 2, 2021 06:57

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04ae485

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Merge branch 'master' into 8265602-dump-loaded-class-list-custom-loader

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8265602: -XX:DumpLoadedClassList should support custom loaders #4952

8265602: -XX:DumpLoadedClassList should support custom loaders #4952

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		void ClassListWriter::write(const InstanceKlass* k, const ClassFileStream* cfs) {
		assert(is_enabled(), "must be");

8265602: -XX:DumpLoadedClassList should support custom loaders #4952

8265602: -XX:DumpLoadedClassList should support custom loaders #4952

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