RFR: 8278268 - (ch) InputStream returned by Channels.newInputStream should have fast path for FileChannel targets [v17]

[Alan Bateman]

On Sun, 11 Dec 2022 15:18:54 GMT, Markus KARG <duke at openjdk.org> wrote:

>> This sub-issue defines the work to be done to implement JDK-8265891 solely for the particular case of FileChannel.transferFrom(ReadableByteChannel), including special treatment of SelectableByteChannel.
>
> Markus KARG has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains one commit:
> 
>   Implementing 8278268
>   
>   Signed-off-by: Markus Karg <markus at headcrashing.eu>

Which platform was used to generate the performance data? Also what was the source stream? Just asking as FileChannel.transferFrom uses copy_file_range for file-to-file (Linux), memory mapping for file-to-file, and a copy loop for other cases.

In any case, the changes to ChannelInputStream.transferTo does the right thing. Most of the change in the PR is the tests. I don't have time to look at those closely right now but Lance or Brian might have cycles.

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PR: https://git.openjdk.org/jdk/pull/6711