Integrated: 8276779: (ch) InputStream returned by Channels.newInputStream should have fast path for SelectableChannels

[Markus KARG]

On Thu, 19 Aug 2021 06:16:42 GMT, Markus KARG <duke at openjdk.java.net> wrote:

> As proposed in JDK-8265891, this PR provides an implementation for `Channels.newInputStream().transferTo()` which provide superior performance compared to the current implementation. This PR is a spin-off from https://github.com/openjdk/jdk/pull/4263 and deliberately concentrates **only** on `FileChannel`s. Other types of channels will be discussed in future PRs.
> 
> * 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 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. A rather similar approach in different use casse was recently implemented by https://github.com/openjdk/jdk/pull/5097 which was reported by even provide 5x performance (https://github.com/openjdk/jdk/pull/5097#issuecomment-897271997).
> 
> **Update:** This sub-issue *only* defines the work to be done to implement JDK-8265891 *solely* for the particular case of FileChannel.transferTo(WriteableByteChannel), including special treatment of SelectableByteChannel, as the `master` branch already contains code to handle the specific case of FileChannel.transferTo(FileChannel).

This pull request has now been integrated.

Changeset: 9642629d
Author:    Markus Karg <markus at headcrashing.eu>
Committer: Alan Bateman <alanb at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/9642629d15d9631d8da9a3abdabc40323f3c774b
Stats:     110 lines in 3 files changed: 99 ins; 0 del; 11 mod

8276779: (ch) InputStream returned by Channels.newInputStream should have fast path for SelectableChannels

Reviewed-by: lancea, alanb

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PR: https://git.openjdk.java.net/jdk/pull/5179