RFR: 8264644: More complete ClassLoaderData for cld->print() [v2]

Yi Yang yyang at openjdk.java.net
Fri Apr 2 16:18:25 UTC 2021 

On Fri, 2 Apr 2021 15:00:46 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Hi @coleenp, thanks for looking at this, it does outputs too detailed content for klasses(actually that's what I want to see), if you think it is too much detail for most people, I can print detailed content of klasses of CLD only when -XX:+Verbose.
>> ...
>> ClassLoaderData(0x00007fea483e5a50)
>>  - name                'app'
>>  - holder              WeakHandle: 0x00000007fef56d98
>>  - class loader        0x7fea483e5c08
>>  - metaspace           (nil)
>>  - unloading           false
>>  - class mirror holder false
>>  - modified oops       true
>>  - keep alive          0
>>  - claim               none
>>  - handles             20
>>  - dependency count    0
>>  - klasses             { }
>>  - packages            0x7fea483e5df0
>>  - module              0x7fea483ea640
>>  - unnamed module      0x7fea483e65a0
>>  - dictionary          0x7fea483e6640
>>  - deallocate list     (nil)
>> ClassLoaderData(0x00007fea482ee640)
>>  - name                'platform'
>>  - holder              WeakHandle: 0x00000007fef56678
>>  - class loader        0x7fea482ee7f8
>>  - metaspace           (nil)
>>  - unloading           false
>>  - class mirror holder false
>>  - modified oops       true
>>  - keep alive          0
>>  - claim               none
>>  - handles             24
>>  - dependency count    0
>>  - klasses             { }
>>  - packages            0x7fea482eebf0
>>  - module              0x7fea482ef4f0
>>  - unnamed module      0x7fea482ef3a0
>>  - dictionary          0x7fea482ef440
>>  - deallocate list     (nil)
>> ClassLoaderData(0x00007fea482e01f0)
>>  - name                'bootstrap'
>>  - class loader        (nil)
>>  - metaspace           0x7fea48391b60
>>  - unloading           false
>>  - class mirror holder false
>>  - modified oops       true
>>  - keep alive          1
>>  - claim               none
>>  - handles             668
>>  - dependency count    0
>>  - klasses             {java.lang.Shutdown$Lock,java.lang.Shutdown,[Ljava.nio.charset.CoderResult;,java.nio.charset.CoderResult,java.nio.HeapCharBuffer,java.nio.CharBuffer,java.lang.Readable,java.lang.invoke.StringConcatFactory$3,java.lang.invoke.StringConcatFactory$2,java.lang.invoke.StringConcatFactory$1,java.lang.invoke.StringConcatFactory,jdk.internal.util.Preconditions,sun.net.util.IPAddressUtil,sun.net.www.protocol.file.Handler,java.net.URLStreamHandler,java.util.HexFormat,sun.net.www.ParseUtil,[Ljava.io.File$PathStatus;,java.io.File$PathStatus,java.net.URL$3,jdk.internal.access.JavaNetURLAccess,java.net.URL$DefaultFactory,java.net.URLStreamHandlerFactory,jdk.internal.loader.URLClassPath,jdk.internal.loader.BootLoader,java.util.ArrayDeque,java.util.Deque,java.util.Queue,jdk.internal.loader.NativeLibraries$2,jdk.internal.loader.NativeLibraries$NativeLibraryImpl,jdk.internal.loader.NativeLibrary,java.security.ProtectionDomain$JavaSecurityAccessImpl,jdk.internal.access.JavaSecu
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 $ByteCache,java.lang.Long$LongCache,java.lang.Integer$IntegerCache,jdk.internal.vm.vector.VectorSupport$VectorShuffle,jdk.internal.vm.vector.VectorSupport$VectorMask,jdk.internal.vm.vector.VectorSupport$Vector,jdk.internal.vm.vector.VectorSupport$VectorPayload,jdk.internal.vm.vector.VectorSupport,java.lang.reflect.RecordComponent,java.util.Iterator,[Ljava.lang.Long;,java.lang.Long,[Ljava.lang.Integer;,java.lang.Integer,[Ljava.lang.Short;,java.lang.Short,[Ljava.lang.Byte;,java.lang.Byte,java.lang.Double,java.lang.Float,[Ljava.lang.Number;,java.lang.Number,[Ljava.lang.Character;,java.lang.Character,java.lang.Boolean,java.util.concurrent.locks.AbstractOwnableSynchronizer,java.lang.LiveStackFrameInfo,java.lang.LiveStackFrame,java.lang.StackFrameInfo,java.lang.StackWalker$StackFrame,java.lang.StackStreamFactory$AbstractStackWalker,java.lang.StackWalker,java.nio.Buffer,[Ljava.lang.StackTraceElement;,java.lang.StackTraceElement,java.util.ArrayList,java.util.RandomAccess,java.util.AbstractL
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 [Ljava.lang.reflect.Type;,java.lang.reflect.Type,[Ljava.lang.reflect.GenericDeclaration;,java.lang.reflect.GenericDeclaration,[Ljava.lang.reflect.AnnotatedElement;,java.lang.reflect.AnnotatedElement,[Ljava.lang.String;,java.lang.String,[Ljava.lang.constant.ConstantDesc;,java.lang.constant.ConstantDesc,[Ljava.lang.constant.Constable;,java.lang.constant.Constable,[Ljava.lang.CharSequence;,java.lang.CharSequence,[Ljava.lang.Comparable;,java.lang.Comparable,[Ljava.io.Serializable;,java.io.Serializable,[[Ljava.lang.Object;,[Ljava.lang.Object;,java.lang.Object, }
>>  - packages            0x7fea482e03a0
>>  - module              0x7fea482e5030
>>  - unnamed module      0x7fea482e0b50
>>  - dictionary          0x7fea482e0bf0
>>  - jmethod count       3
>>  - deallocate list     (nil)
>
> I was just using PrintSystemDictionaryAtExit and wanted to ignore the CLDG information, which is already quite verbose for this option, so there was a lot of scrolling.
> 
> It's sort of a small change to add a nonproduct PrintClassLoaderDataGraphAtExit and use that to print the CLDG at exit and remove it from PrintSystemDictionaryAtExit.  Then we can each get the info we want.

While adding the new flag PrintSystemDictionaryAtExit, I found that we may have missed acquiring CLDGraph_lock in some places.

https://github.com/openjdk/jdk/blob/177bc84fe861f93f51e6d8ab5bf0738f4009522a/src/hotspot/share/classfile/classLoaderDataGraph.cpp#L674-L676

https://github.com/openjdk/jdk/blob/177bc84fe861f93f51e6d8ab5bf0738f4009522a/src/hotspot/share/memory/universe.cpp#L1129-L1131

It seems they are neither at a safepoint nor owned the CLDGraph_lock?

Thanks!
Yang

-------------

PR: https://git.openjdk.java.net/jdk/pull/3323

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