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

[Alan Bateman]

On Wed, 15 Jun 2022 00:20:58 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.

src/java.base/unix/classes/sun/nio/fs/UnixCopyFile.java line 276:

> 274:                     long bss = Files.getFileStore(source).getBlockSize();
> 275:                     long bst = Files.getFileStore(target).getBlockSize();
> 276:                     if (bss > 0 && bst > 0) {

This should be UnixFileStoreAttributes.get(source).blockSize() to avoid calling from the provider to the API or needing to create a FileStore.

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