RFR: 6980847: (fs) Files.copy needs to be tuned [v5]

[Alan Bateman]

On Thu, 16 Jun 2022 23:36:34 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>> Modify `UnixCopyFile.copyFile()` to set the transfer size to the least common multiple of the source and destination file block sizes if the block sizes are not equal. Modify `WindowsFileCopy.copy()` to set `COPY_FILE_NO_BUFFERING` in the flags passed to `CopyFileEx()` if the size of the transfer is greater than a threshold.
>
> Brian Burkhalter has updated the pull request incrementally with one additional commit since the last revision:
> 
>   6980847: Use temporary direct buffer for user-space copy

src/java.base/windows/classes/sun/nio/fs/WindowsFileCopy.java line 186:

> 184:             }
> 185:             final int flags = ((!followLinks) ? COPY_FILE_COPY_SYMLINK : 0) |
> 186:                 ((size > UNBUFFERED_IO_THRESHOLD) ? COPY_FILE_NO_BUFFERING : 0);

The size of the source file is already in sourceAttrs.size(), no need to call back into the API to access the file again.

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PR: https://git.openjdk.org/jdk/pull/9161