Are there any user space tools (other than our test tools and xfs_io etc.) that support copy_file_range? Looks like at least cp and rsync and dd don't. That syscall which now has been around a couple years, and was reminded about at the LSF/MM summit a few days ago, presumably is the 'best' way to copy a file fast since it tries all the mechanisms (reflink etc.) in order. Since copy_file_range syscall can be 100x or more faster for network file systems than the alternative, was surprised when I noticed that cp and rsync didn't support it. It doesn't look like rsync even supports reflink either(although presumably if you call copy_file_range you don't have to worry about that), and reads/writes are 8K. See copy_file() in rsync/util.c In the cp command it looks like it can call the FICLONE IOCTL (see clone_file() in coreutils/src/copy.c) but doesn't call the expected "copy_file_range" syscall. In the dd command it doesn't call either - see dd_copy in corutils/src/dd.c Since it can be 100x or more faster in some cases to call copy_file_range than do reads/writes back and forth to do a copy (especially if network or clustered backend or cloud), what tools are the best to recommend? Would rsync or cp be likely to take patches to call the standard "copy_file_range" syscall (http://man7.org/linux/man-pages/man2/copy_file_range.2.html)? Presumably not if it has been two+ years ... but would be interested what copy tools to recommend to use instead. These are not uncommon cases (all Windows, Macs, Samba etc. and even some NFS servers) ... but copies over local file systems can benefit too (as copy_file_range tries various mechanisms). -- Thanks, Steve
