8275729: Qualified method names in CodeHeap Analytics #6200

eastig · 2021-11-01T20:51:39Z

This PR changes nmethods names in METHOD NAMES for CodeHeap section to be qualified.
Testing:

make test TEST="gtest": Passed
make run-test TEST="tier1": Passed
make run-test TEST="tier2": Passed
make run-test TEST=serviceability/dcmd/compiler/CodeHeapAnalyticsMethodNames.java: Passed

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Issue

JDK-8275729: Qualified method names in CodeHeap Analytics

Reviewers

Yi Yang (@kelthuzadx - Committer)
Tobias Hartmann (@TobiHartmann - Reviewer)

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bridgekeeper · 2021-11-01T20:52:01Z

👋 Welcome back eastig! 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 · 2021-11-01T20:55:19Z

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

hotspot-compiler
serviceability

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mlbridge · 2021-11-01T21:00:28Z

Webrevs

00: Full (bba8ae3a)

y1yang0

This looks good now. Old output can not tell us which class the method belongs to.

Old:
0x00007f6e91063010 (+0x00000010) 0x000000a0(   0K)  none   0    480 nMethod (deopt)     nmethod
0x00007f6e91063310 (+0x00000310) 0x000000f8(   0K)  none   0    480 nMethod (active)    name()Ljava/lang/String;
0x00007f6e91063610 (+0x00000610) 0x000000f8(   0K)  none   0    480 nMethod (active)    descriptor()Ljava/lang/module/ModuleDescriptor;
0x00007f6e91063910 (+0x00000910) 0x00000000(   0K)  none   0    480 nMethod (active)    getReferenceVolatile(Ljava/lang/Object;J)Ljava/lang/Object;
0x00007f6e91063d90 (+0x00000d90) 0x00000000(   0K)  none   0    480 nMethod (active)    hashCode()I
0x00007f6e91064190 (+0x00001190) 0x000000f8(   0K)    c1   1    480 nMethod (active)    name()Ljava/lang/String;
0x00007f6e91064490 (+0x00001490) 0x000000f8(   0K)    c1   1    480 nMethod (active)    modifiers()Ljava/util/Set;
0x00007f6e91064790 (+0x00001790) 0x000000f8(   0K)    c1   1    480 nMethod (active)    targets()Ljava/util/Set;
0x00007f6e91064a90 (+0x00001a90) 0x000000f8(   0K)    c1   1    480 nMethod (active)    source()Ljava/lang/String;
0x00007f6e91064d90 (+0x00001d90) 0x000000f8(   0K)    c1   1    480 nMethod (active)    isEmpty()Z
New:

0x00007f08adc94010 (+0x00000010) 0x00000150(   0K)    c1   3    480 nMethod (deopt)     nmethod
0x00007f08adc94390 (+0x00000390) 0x000001b0(   0K)    c1   3    480 nMethod (active)    java.lang.String.isLatin1()Z
0x00007f08adc94710 (+0x00000710) 0x00000258(   0K)    c1   3    480 nMethod (active)    jdk.internal.util.Preconditions.checkIndex(IILjava/util/function/BiFunction;)I
0x00007f08adc94b90 (+0x00000b90) 0x000004e8(   1K)    c1   3    480 nMethod (deopt)     nmethod
0x00007f08adc95310 (+0x00001310) 0x00000298(   0K)    c1   3    480 nMethod (active)    java.lang.StringLatin1.charAt([BI)C
0x00007f08adc95790 (+0x00001790) 0x000001a0(   0K)    c1   3    480 nMethod (active)    java.lang.String.checkIndex(II)V
0x00007f08adc95b10 (+0x00001b10) 0x00000170(   0K)    c1   3    480 nMethod (active)    java.lang.String.coder()B
0x00007f08adc95e90 (+0x00001e90) 0x000003e8(   0K)    c1   3    480 nMethod (active)    java.lang.String.hashCode()I
0x00007f08adc96490 (+0x00002490) 0x00000130(   0K)    c1   3    480 nMethod (deopt)     nmethod
0x00007f08adc96790 (+0x00002790) 0x00000210(   0K)    c1   3    480 nMethod (active)    java.lang.String.length()I

TobiHartmann

Looks good to me.

openjdk · 2021-11-02T11:00:19Z

@eastig 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:

8275729: Qualified method names in CodeHeap Analytics

Reviewed-by: yyang, thartmann

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 101 new commits pushed to the master branch:

8630f55: 8275406: Add copy-to-clipboard feature to snippet UI
9971a2c: 8275735: [linux] Remove deprecated Metrics api (kernel memory limit)
b7a06be: 8252990: Intrinsify Unsafe.storeStoreFence
92be9d8: 8276236: Table headers missing in Formatter api docs
9bf3165: 8276164: RandomAccessFile#write method could throw IndexOutOfBoundsException that is not described in javadoc
0488ebd: 8276105: C2: Conv(D|F)2(I|L)Nodes::Ideal should handle rounding correctly
acceffc: 8273704: DrawStringWithInfiniteXform.java failed : drawString with InfiniteXform transform takes long time
2eafa03: 8276234: Trivially clean up locale-related code
47e7a42: 8262945: [macos] Regression Manual Test for Key Events Fails
99b7b95: 8276205: Shenandoah: CodeCache_lock should always be held for initializing code cache iteration
... and 91 more: https://git.openjdk.java.net/jdk/compare/0bcc1749eaea20cb983a983073ad33d305681879...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@kelthuzadx, @TobiHartmann) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

eastig · 2021-11-02T12:14:01Z

/integrate

openjdk · 2021-11-02T12:15:17Z

@eastig
Your change (at version bba8ae3) is now ready to be sponsored by a Committer.

phohensee · 2021-11-02T16:30:03Z

/sponsor

openjdk · 2021-11-02T16:32:14Z

Going to push as commit 8fc16f1.
Since your change was applied there have been 106 commits pushed to the master branch:

fa4ce82: 8276260: (se) Remove java/nio/channels/Selector/Wakeup.java from ProblemList (win)
495c828: 8276188: Clarify "default charset" descriptions in String class
cd778f5: 8202667: java/awt/Debug/DumpOnKey/DumpOnKey.java times out on Windows
b889f2a: 8276175: codestrings.validate_vm gtest still broken on ppc64 after JDK-8276046
5b4e398: 8275766: (tz) Update Timezone Data to 2021e
8630f55: 8275406: Add copy-to-clipboard feature to snippet UI
9971a2c: 8275735: [linux] Remove deprecated Metrics api (kernel memory limit)
b7a06be: 8252990: Intrinsify Unsafe.storeStoreFence
92be9d8: 8276236: Table headers missing in Formatter api docs
9bf3165: 8276164: RandomAccessFile#write method could throw IndexOutOfBoundsException that is not described in javadoc
... and 96 more: https://git.openjdk.java.net/jdk/compare/0bcc1749eaea20cb983a983073ad33d305681879...master

Your commit was automatically rebased without conflicts.

openjdk · 2021-11-02T16:32:33Z

@phohensee @eastig Pushed as commit 8fc16f1.

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

simonis · 2021-11-02T16:34:34Z

src/hotspot/share/code/codeHeapState.cpp

@@ -2334,6 +2335,11 @@ void CodeHeapState::print_names(outputStream* out, CodeHeap* heap) {
            Symbol* methSig   = method->signature();
            const char*   methSigS  = (methSig  == NULL) ? NULL : methSig->as_C_string();
            methSigS  = (methSigS  == NULL) ? "<method signature unavailable>" : methSigS;
+
+            Klass* klass = method->method_holder();
+            assert(klass->is_loader_alive(), "must be alive");


Are you sure klass is always valid here and that its class loader has to be alive (i.e. the corresponding class hasn't been unloaded in the meantime)?

In https://bugs.openjdk.java.net/browse/JDK-8275729 you say that the Top50 list already has qualified names but as far as I know, that information is already collected in the aggregation step where it is safe. You now query this information in the reporting step.

I know we had problems due to access to dead methods before (see JDK-8219586: CodeHeap State Analytics processes dead nmethods and I just want to make sure we don't re-introduce such problems.

Maybe @RealLucy or @fisk can have an additional look?

@simonis
The code is guarded by checks:

// access nmethod and Method fields only if we own the CodeCache_lock. // This fact is implicitly transported via nm != NULL. if (nmethod_access_is_safe(nm)) { ... bool get_name = (cbType == nMethod_inuse) || (cbType == nMethod_notused); ... if (get_name) {

I was thinking whether I should use if (klass->is_loader_alive()) or assert(klass->is_loader_alive()). I chose the assert because if it is safe to access Method than its holder Klass must be alive.

Hi,
the code is safe. Not because of the checks cited by @eastig but because print_names() is only called if the required locks (Compile_lock and CodeCache_lock) have been continuously held since the aggregation step. See src/hotspot/share/compiler/compileBroker.cpp. A lot of effort has been spent to be less restrictive on print_names(), with no success.
Thanks for the enhancement.

phohensee · 2021-11-02T16:38:58Z

Volker, I sponsored this before you posted your review. Evgeny, if it's a problem, please file a bug.

simonis · 2021-11-02T16:40:05Z

No problem, I know I was late :)
But I also know that this is a sensitive area, so better double check...

eastig · 2021-11-02T18:11:06Z

Thanks for reviewing @kelthuzadx and @TobiHartmann.

RealLucy

To me, the change looks good.

RealLucy · 2021-11-02T20:54:29Z

src/hotspot/share/code/codeHeapState.cpp

@@ -2334,6 +2335,11 @@ void CodeHeapState::print_names(outputStream* out, CodeHeap* heap) {
            Symbol* methSig   = method->signature();
            const char*   methSigS  = (methSig  == NULL) ? NULL : methSig->as_C_string();
            methSigS  = (methSigS  == NULL) ? "<method signature unavailable>" : methSigS;
+
+            Klass* klass = method->method_holder();
+            assert(klass->is_loader_alive(), "must be alive");


Hi,
the code is safe. Not because of the checks cited by @eastig but because print_names() is only called if the required locks (Compile_lock and CodeCache_lock) have been continuously held since the aggregation step. See src/hotspot/share/compiler/compileBroker.cpp. A lot of effort has been spent to be less restrictive on print_names(), with no success.
Thanks for the enhancement.

vnkozlov · 2021-11-02T21:53:38Z

The change caused failure in our testing: https://bugs.openjdk.java.net/browse/JDK-8276429

vnkozlov · 2021-11-02T22:05:01Z

I don't think we need this assert just to print klass's name.
May be follow the code pattern for method's name and signature.

eastig · 2021-11-02T22:49:15Z

I don't think we need this assert just to print klass's name. May be follow the code pattern for method's name and signature.

Agree. I'll submit PR with the code:

Symbol* className = klass->name();
const char*   classNameS = (className == nullptr) ? nullptr : className->external_name();
classNameS = (classNameS == nullptr) ? "<class name unavailable>" : classNameS;
ast->print("%s.", classNameS);

vnkozlov · 2021-11-02T22:57:23Z

Yes, I am currently testing similar fix:

-            Klass* klass = method->method_holder();
-            assert(klass->is_loader_alive(), "must be alive");
+            Klass* methHolder = method->method_holder();
+            const char*    methHolderS  = (methHolder  == NULL) ? NULL : methHolder->external_name();
+            methHolderS = (methHolderS  == NULL) ? "<method holder name unavailable>" : methHolderS;
 
-            ast->print("%s.", klass->external_name());
+            ast->print("%s.", methHolderS);

Note, failed test is closed so I have to run testing.

eastig · 2021-11-02T23:03:22Z

Yes, I am currently testing similar fix:

-            Klass* klass = method->method_holder();
-            assert(klass->is_loader_alive(), "must be alive");
+            Klass* methHolder = method->method_holder();
+            const char*    methHolderS  = (methHolder  == NULL) ? NULL : methHolder->external_name();
+            methHolderS = (methHolderS  == NULL) ? "<method holder name unavailable>" : methHolderS;
 
-            ast->print("%s.", klass->external_name());
+            ast->print("%s.", methHolderS);

Note, failed test is closed so I have to run testing.

Is NULL method holder an acceptable situation? Could it be a sign of a bug?
BTW, Klass::external_name() returns <unknown> if Klass::name() is NULL.

vnkozlov · 2021-11-02T23:15:36Z

Is NULL method holder an acceptable situation? Could it be a sign of a bug?

You are right, all methods should have class holders. I just followed code pattern.

BTW, Klass::external_name() returns <unknown> if Klass::name() is NULL.

I see, you want to have the same string instead of <unknown>. Reasonable.

I will test your changes too. File PR and I will review and post testing results.

vnkozlov · 2021-11-02T23:17:30Z

BTW, you need to update Copyright year in file.

eastig · 2021-11-03T14:22:11Z

@vnkozlov Created PR #6234

8275729: Qualified method names in CodeHeap Analytics

bba8ae3

openjdk bot added the rfr Pull request is ready for review label Nov 1, 2021

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8275729: Qualified method names in CodeHeap Analytics #6200

8275729: Qualified method names in CodeHeap Analytics #6200

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8275729: Qualified method names in CodeHeap Analytics #6200

8275729: Qualified method names in CodeHeap Analytics #6200

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eastig commented Nov 1, 2021 • edited by openjdk bot

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