Hi Darrick,
Thanks for your quick and detailed reply.
The thing that really puzzled me when I re-ran Suyash's experiments on a
DRAM-backed file system is that the ioctl(FICLONE) calls were still very
very slow. A slow block storage device can't be blamed, because there
wasn't a slow block storage device anywhere in the picture; the slowness
came from software.
Suyash, can you send those results?
-- Terence Kelly
On Tue, 13 Dec 2022, Darrick J. Wong wrote:
FICLONE (at least on XFS) persists dirty pagecache data to disk, and
then duplicates all written-space mapping records from the source file
to the destination file. It skips preallocated mappings created with
fallocate.
So yes, the plot is exactly what I was expecting.
