On Sun, 1 Aug 2021 22:01:33 GMT, Markus KARG <d...@openjdk.java.net> wrote:

>> This PR-*draft* is **work in progress** and an invitation to discuss a 
>> possible solution for issue 
>> [JDK-8265891](https://bugs.openjdk.java.net/browse/JDK-8265891). It is *not 
>> yet* intended for a final review.
>> As proposed in JDK-8265891, this PR provides an implementation for 
>> `Channels.newInputStream().transferTo()` which provide superior performance 
>> compared to the current implementation. The changes are:
>> * Prevents transfers through the JVM heap as much as possibly by offloading 
>> to deeper levels via NIO, hence allowing the operating system to optimize 
>> the transfer.
>> * Using more JRE heap in the fallback case when no NIO is possible (still 
>> only KiBs, hence mostl ynegligible even on SBCs) to better perform on modern 
>> hardware / fast I/O devides.
>> Using JMH I have benchmarked both, the original implementation and this 
>> implementation, and (depending on the used hardware and use case) 
>> performance change was approx. doubled performance. So this PoC proofs that 
>> it makes sense to finalize this work and turn it into an actual OpenJDK 
>> contribution. 
>> I encourage everybody to discuss this draft:
>> * Are there valid arguments for *not* doing this change?
>> * Is there a *better* way to improve performance of 
>> `Channels.newInputStream().transferTo()`?
>> * How to go on from here: What is missing to get this ready for an actual 
>> review?
> 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

Please keep this PR open; I will continune work on it soon.


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

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