RFR: 8262386: resourcehogs/serviceability/sa/TestHeapDumpForLargeArray.java timed out [v14]

[Serguei Spitsyn]

On Thu, 26 Aug 2021 04:27:36 GMT, Lin Zang <lzang at openjdk.org> wrote:

>> src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java line 1367:
>> 
>>> 1365:         @Override
>>> 1366:         public synchronized void write(int b) throws IOException {
>>> 1367:            if (segmentMode && !unbufferedMode) {
>> 
>> It is not clear why the condition` !unbufferedMode` is additionally checked here and several places below. The `SegmentedOutputStream` constructor always sets `false` to the`unbufferedMode` field at L1344. Is it possible that `segmentMode` can be also unbuffered?
>
> The `unbufferedMode` is set to true at L1498, and it is use when writing array data. The purpose is to write the data directly to the file instead of buffering them first, it can avoid memory copy and also avoid timeout when dumping large array (because the buffer must contains the whole segment before it is written to file, to avoid data pollution for compressed dump, and if the buffer is not enough, a memory copy is conducted)

Okay, thanks.

>> src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/utilities/HeapHprofBinWriter.java line 1580:
>> 
>>> 1578:         private boolean allowSegmented;
>>> 1579:         // Write data directly to underlying stream. Don't use internal buffer.
>>> 1580:         private boolean unbufferedMode;
>> 
>> I would suggest replace `unbufferedMode` with `bufferedMode` field. It will simplify logic a little bit.
>> Then you will need to rename the method `fillSegmentSizeAndEnableUnbufferedMode` to be `fillSegmentSizeAndDisableBufferedMode`. 
>> There are several places where `!unbufferedMode` will be replaced with `bufferedMode` .
>
> Good idea, I will made the change. Thanks.

Lin, I'm okay with your fix in general and will approve it after check of your change for the above suggestion.

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

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