8294698: Remove unused 'checkedExceptions' param from MethodAccessorGenerator.generateMethod() #10526

stsypanov · 2022-10-02T20:45:02Z

checkedExceptions param of MethodAccessorGenerator.generateMethod() is unused and should be removed in order to prevent allocations from Method.getExceptionTypes()

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JDK-8294698: Remove unused 'checkedExceptions' param from MethodAccessorGenerator.generateMethod()

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Claes Redestad (@cl4es - Reviewer)

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…enerator.generateMethod()

bridgekeeper · 2022-10-02T20:45:29Z

👋 Welcome back stsypanov! 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 · 2022-10-02T20:54:01Z

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mlbridge · 2022-10-02T20:57:11Z

Webrevs

00: Full (aa7ef3ac)

cl4es · 2022-10-02T22:16:46Z

Seems reasonable, although these generators should only rarely be used when doing reflection. I'm curious if you have some test or micro where the improvement shows?

stsypanov · 2022-10-03T08:05:05Z

@cl4es this code is frequently invoked in Spring-based applications at start-up time. I couldn't design the benchmark for this particular case, assuming that in majority of cases Method.getExceptionTypes() returns a copy of an empty array I think we save about 12 ns and 16 bytes:

@State(Scope.Thread)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@BenchmarkMode(value = Mode.AverageTime)
public class ArrayCloneBenchmark {
  private final Object[] array = new Object[0];

  @Benchmark
  public Object[] cloneArray() {
    return array.clone();
  }
}

Benchmark                                                        Mode  Cnt    Score    Error   Units
ArrayCloneBenchmark.cloneArray                                   avgt   20   12,713 ±  0,484   ns/op
ArrayCloneBenchmark.cloneArray:·gc.alloc.rate                    avgt   20  800,247 ± 29,584  MB/sec
ArrayCloneBenchmark.cloneArray:·gc.alloc.rate.norm               avgt   20   16,004 ±  0,001    B/op
ArrayCloneBenchmark.cloneArray:·gc.churn.G1_Eden_Space           avgt   20  804,623 ± 38,424  MB/sec
ArrayCloneBenchmark.cloneArray:·gc.churn.G1_Eden_Space.norm      avgt   20   16,091 ±  0,455    B/op
ArrayCloneBenchmark.cloneArray:·gc.churn.G1_Survivor_Space       avgt   20    0,006 ±  0,002  MB/sec
ArrayCloneBenchmark.cloneArray:·gc.churn.G1_Survivor_Space.norm  avgt   20   ≈ 10⁻⁴             B/op
ArrayCloneBenchmark.cloneArray:·gc.count                         avgt   20  286,000           counts
ArrayCloneBenchmark.cloneArray:·gc.time                          avgt   20  171,000               ms

cl4es · 2022-10-03T11:03:48Z

I agree that getting rid of the clone can help -- but since JEP 416 the generators modified here is mostly a fallback and the bulk of the use will use MethodHandles (unless you disable JEP 416 and fall back to the legacy impl). I was mostly curious if you had a startup or other benchmark running on mainline where the change you're doing here could be observed.

cl4es · 2022-10-03T11:10:11Z

Approving since changes are trivial and having less code never hurts

openjdk · 2022-10-03T11:10:27Z

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openjdk · 2022-10-03T11:10:29Z

@stsypanov 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:

8294698: Remove unused 'checkedExceptions' param from MethodAccessorGenerator.generateMethod()

Reviewed-by: redestad

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 8 new commits pushed to the master branch:

ccc1d31: 8294529: IGV: Highlight the current graphs in the Outline
08a7ecf: 8294671: Remove unused CardValues::last_card
5fe837a: 8294236: [IR Framework] CPU preconditions are overriden by regular preconditions
8e9cfeb: 8294431: jshell reports error on initialisation of static final field of anonymous class
6e8f038: 8294567: IGV: IllegalStateException in search
bc668b9: 8293099: JFR: Typo in TestRemoteDump.java
03f25a9: 8293562: blocked threads with KeepAliveCache.get
a69ee85: 8292336: JFR: Warn users if -XX:StartFlightRecording:disk=false is specified with maxage or maxsize

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stsypanov · 2022-10-03T11:51:32Z

/integrate

openjdk · 2022-10-03T11:53:54Z

@stsypanov
Your change (at version aa7ef3a) is now ready to be sponsored by a Committer.

cl4es · 2022-10-03T12:55:58Z

/sponsor

openjdk · 2022-10-03T12:56:59Z

Going to push as commit 46633e6.
Since your change was applied there have been 9 commits pushed to the master branch:

f2a32d9: 8293691: converting a defined BasicType value to a string should not crash the VM
ccc1d31: 8294529: IGV: Highlight the current graphs in the Outline
08a7ecf: 8294671: Remove unused CardValues::last_card
5fe837a: 8294236: [IR Framework] CPU preconditions are overriden by regular preconditions
8e9cfeb: 8294431: jshell reports error on initialisation of static final field of anonymous class
6e8f038: 8294567: IGV: IllegalStateException in search
bc668b9: 8293099: JFR: Typo in TestRemoteDump.java
03f25a9: 8293562: blocked threads with KeepAliveCache.get
a69ee85: 8292336: JFR: Warn users if -XX:StartFlightRecording:disk=false is specified with maxage or maxsize

Your commit was automatically rebased without conflicts.

openjdk · 2022-10-03T12:57:16Z

@cl4es @stsypanov Pushed as commit 46633e6.

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

mlchung · 2022-10-03T16:44:56Z

I agree that getting rid of the clone can help -- but since JEP 416 the generators modified here is mostly a fallback and the bulk of the use will use MethodHandles (unless you disable JEP 416 and fall back to the legacy impl). I was mostly curious if you had a startup or other benchmark running on mainline where the change you're doing here could be observed.

@stsypanov like @cl4es said, I expect these dynamically generated methods should only be generated during very early VM startup. Once the module system is initialized, it will use method handles.

How do you run the spring-based applications when you observe these methods being called? While this change is trivial and no harm to include this change, this code is planned to be removed in a future release.

stsypanov · 2022-10-04T11:41:31Z

@mlchung I can put here a stack trace of the application invoking the code if you are interested

cl4es · 2022-10-04T11:55:02Z

@stsypanov would be helpful to understand when this code still gets executed. Also note that JEP 416 was integrated in JDK 18 so some details about the runtime would be necessary to get a complete picture.

stsypanov · 2022-10-04T21:54:28Z

@cl4es @mlchung here's the stacktrace of my app running on Java 19:

generate:136, MethodAccessorGenerator (jdk.internal.reflect)
generateSerializationConstructor:107, MethodAccessorGenerator (jdk.internal.reflect)
generateConstructor:420, ReflectionFactory (jdk.internal.reflect)
newConstructorForSerialization:412, ReflectionFactory (jdk.internal.reflect)
getSerializableConstructor:1444, ObjectStreamClass (java.io)
run:412, ObjectStreamClass$2 (java.io)
run:384, ObjectStreamClass$2 (java.io)
executePrivileged:778, AccessController (java.security)
doPrivileged:319, AccessController (java.security)
<init>:384, ObjectStreamClass (java.io)
computeValue:110, ObjectStreamClass$Caches$1 (java.io)
computeValue:107, ObjectStreamClass$Caches$1 (java.io)
computeValue:73, ClassCache$1 (java.io)
computeValue:70, ClassCache$1 (java.io)
getFromHashMap:229, ClassValue (java.lang)
getFromBackup:211, ClassValue (java.lang)
get:117, ClassValue (java.lang)
get:84, ClassCache (java.io)
lookup:363, ObjectStreamClass (java.io)
lookup:246, ObjectStreamClass (java.io)
<clinit>:27, Result (org.junit.runner)
run:132, JUnitCore (org.junit.runner)
startRunnerWithArgs:69, JUnit4IdeaTestRunner (com.intellij.junit4)
execute:38, IdeaTestRunner$Repeater$1 (com.intellij.rt.junit)
repeat:11, TestsRepeater (com.intellij.rt.execution.junit)
startRunnerWithArgs:35, IdeaTestRunner$Repeater (com.intellij.rt.junit)
prepareStreamsAndStart:235, JUnitStarter (com.intellij.rt.junit)
main:54, JUnitStarter (com.intellij.rt.junit)

mlchung · 2022-10-04T21:58:00Z

Thanks. This is for serialization and not the use of the core reflection which is what JEP 416 covered.

stsypanov · 2022-10-04T22:00:15Z

Is it going to be covered with new reflection sometimes? You mentioned above that "this code is planned to be removed in a future release" so some substitution must be provided, right?

8294698: Remove unused 'checkedExceptions' param from MethodAccessorG…

aa7ef3a

…enerator.generateMethod()

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stsypanov deleted the 8294698 branch October 3, 2022 13:11

8294698: Remove unused 'checkedExceptions' param from MethodAccessorGenerator.generateMethod() #10526

8294698: Remove unused 'checkedExceptions' param from MethodAccessorGenerator.generateMethod() #10526

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