RFR: 8286763: [REDO] (fc) Tune FileChannel.transferFrom()

[Brian Burkhalter]

On Tue, 17 May 2022 15:34:50 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> Isn't it that returning `IOS_UNSUPPORTED` would disable it for everyone? I thought that `IOS_UNSUPPORTED_CASE` allows it to be tried again. Of course one could check for append or overlap in the Java layer instead. I actually had it that way initially for the overlap case but removed it.
>
>> Isn't it that returning `IOS_UNSUPPORTED` would disable it for everyone? I thought that `IOS_UNSUPPORTED_CASE` allows it to be tried again. Of course one could check for append or overlap in the Java layer instead. I actually had it that way initially for the overlap case but removed it.
> 
> Oh I see, it's only IOS_UNSUPPORTED that disables it. With IOS_UNSUPPORTED_CASE then you may retry it again.

Correct. It is IOS_UNSUPPORTED for example if the copy_file_range function pointer is NULL (not available via dlsym()). Then of course one can do nothing.

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PR: https://git.openjdk.java.net/jdk/pull/8733