RFR: 8262386: resourcehogs/serviceability/sa/TestHeapDumpForLargeArray.java timed out [v4]

[Chris Plummer]

On Mon, 15 Mar 2021 08:50:35 GMT, Lin Zang <lzang at openjdk.org> wrote:

>> 8262386: resourcehogs/serviceability/sa/TestHeapDumpForLargeArray.java timed out
>
> Lin Zang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:
> 
>  - Merge branch 'master' into sf
>  - Revert "reduce memory consumption"
>    
>    This reverts commit 70e43ddd453724ce36bf729fa6489c0027957b8e.
>  - reduce memory consumption
>  - code refine
>  - 8262386: resourcehogs/serviceability/sa/TestHeapDumpForLargeArray.java timed out

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java line 587:

> 585:         long currentRecordLength = 0;
> 586: 
> 587:         // There is an U4 slot contains the data size written in the dump file.

"a U4 slot that contains..."

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java line 588:

> 586: 
> 587:         // There is an U4 slot contains the data size written in the dump file.
> 588:         // Need to trunicate the array length if the size exceed the MAX_U4_VALUE.

Should be "truncate" and "exceeds"

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java line 618:

> 616:             int bytesToWrite = (int) (longBytes);
> 617:             hprofBufferedOut.fillSegmentSizeAndEnableWriteThrough(bytesToWrite);
> 618:         }

It seems to me this is the key part of the fix, and all other changes and driven by this change. What I don't understand is why enabling `writeThrough` is done here in `calculateArrayMaxLength()`, especially since this same code might be execute more than once for the same segment (thus "enabling" `writeThrough` when it is already enabled). What is the actual trigger for wanting `writeThrough` mode? Is it really just seeing an array for the first time in a segment?

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PR: https://git.openjdk.java.net/jdk/pull/2803