RFR: 8274113: (fc) Tune FileChannel.transferFrom() [v3]

[Alan Bateman]

On Wed, 11 May 2022 17:24:38 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>> This request proposes to change `FileChannel.transferFrom()` to add a fast path on Linux and a threshold for mapped transfers on all platforms.
>
> Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8274113: Invert transferXXXSupported

src/java.base/share/classes/sun/nio/ch/FileChannelImpl.java line 541:

> 539:     // set this to true if we find out later that it doesn't
> 540:     //
> 541:     private static volatile boolean transferToNotSupported = false;

The motive for inverting these flags was to avoid the volatile write, so you can drop "= false" from both flags now.

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PR: https://git.openjdk.java.net/jdk/pull/8644