RFR: 8265891: (ch) InputStream returned by Channels.newInputStream should override transferTo [v13]

[Markus KARG]

On Thu, 12 Aug 2021 01:04:29 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>> Markus KARG has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Draft: Eliminated duplicate code using lambda expressions
>>  - Draft: Use blocking mode also for target channel
>
> src/java.base/share/classes/sun/nio/ch/ChannelInputStream.java line 249:
> 
>> 247:     }
>> 248: 
>> 249:     private static long transfer(ReadableByteChannel src, WritableByteChannel dst) throws IOException {
> 
> Does this method have a measurable improvement in performance over `InputStream.transferTo()`?

Measured it today, here are the actual results:

Sandbox.transferTo  thrpt   25  0,091 ± 0,011  ops/s -- using byte[] (original implementation)
Sandbox.transferTo  thrpt   25  0,095 ± 0,012  ops/s -- using utility temporary buffer (my contribution)
Sandbox.transferTo  thrpt   23  0,099 ± 0,012  ops/s -- FileChannel.transferTo(FileChannel)


The improvement of this method actually is approx. 4% on my Windows laptop, which I would say is worth to do it.

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PR: https://git.openjdk.java.net/jdk/pull/4263