RFR: 8269685: Optimize HeapHprofBinWriter implementation [v8]

[Serguei Spitsyn]

On Thu, 16 Sep 2021 12:26:10 GMT, Lin Zang <lzang at openjdk.org> wrote:

>> This PR rewrite the implementation of the HeapHprofBinWriter, which could simplify the logic of current implementation.
>> please see detail description at https://bugs.openjdk.java.net/browse/JDK-8269685.
>
> Lin Zang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains ten commits:
> 
>  - Merge branch 'master' into hprof
>  - code clean up and refinement
>  - Merge branch 'master' into hprof
>  - make calculateGlobalJNIHandlesDumpRecordSize abstract
>  - code clean up and remove useless methods
>  - Merge branch 'master' into hprof
>  - fix write size issue
>  - Merge branch 'master' into hprof
>  - 8269685: Optimize HeapHprofBinWriter implementation

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java line 495:

> 493:             Klass bottomType = oak.getBottomKlass();
> 494:             if (bottomType instanceof InstanceKlass ||
> 495:                     bottomType instanceof TypeArrayKlass) {

Formatting nit: I'd suggest to align `bottomType` with `bottomType`.

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java line 611:

> 609:         Klass reflectedKlass = java_lang_Class.asKlass(instance);
> 610:         // dump instance record only for primitive type Class objects.
> 611:         // all other Class objects are covered by writeClassDumpRecords.

Formatting nit for 610-611: If the comment is ended with dot then start it from capital a letter.

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java line 642:

> 640:     @Override
> 641:     protected void writeHeapRecordPrologue(int size) throws IOException {
> 642:         if (size == 0 || (currentSegmentStart > 0)) {

Formatting nit: There is no need in internal brackets `()` around `currentSegmentStart > 0`.

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java line 721:

> 719: 
> 720:     // Check if we need to truncate an array.
> 721:     // The limitation is that the size of "heap dump" or "heap dump segment" must be <= MAX_U4_VALUE

Formatting nit: Add dot at the end of comment.

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PR: https://git.openjdk.java.net/jdk/pull/4666