cp(1) of large files is causing 100% CPU utilization and poor transfer

[Alan Somers]

On Sat, Jan 2, 2021 at 11:28 AM Matthias Apitz <guru at unixarea.de> wrote:

> El día sábado, enero 02, 2021 a las 05:06:05p. m. +0000, Rick Macklem
> escribió:
>
> > Just fyi, I've reproduced the problem.
> > All I did was create a 20Gbyte file
> > on UFS on a slow (4Gbyte or RAM,
> > slow spinning disk) laptop.
> > (The UFS file system is just what the installer creates these days.)
> >
> > cp still hasn't finished and is definitely
> > taking a looott longer than dd did.
> >
> > I'll start drilling down later to-day.
> >
> > I'll admit doing lots of testing of copy_file_range(2)
> > with large sparse files, but I may have missed testing
> > a large non-sparse file.
> >
> > rick
> > ps: I've added Kostik and Kirk to the cc.
>
> As the problem seems to be clear now, should I still file a PR?
> I'm happy to do so.
>
>         matthias
>

Yes please .  That will help ensure that we don't lose track of it.