Behaviour of system tray bandwidth indicator

[Marko Vojinovic]

On Thu, 20 Mar 2014 13:14:50 +0100
Reindl Harald <h.reindl at thelounge.net> wrote:

> 
> Am 20.03.2014 12:29, schrieb Patrick O'Callaghan:
> > On Thu, 2014-03-20 at 11:54 +0100, Kevin Kofler wrote:
> >> Patrick O'Callaghan wrote:
> >>> I'm using Dolphin to copy large files (several GB) to an
> >>> NFS-mounted NAS. This works fine except that the informational
> >>> system tray pop-up is showing absurd values for the copy
> >>> bandwidth. e.g. a 2GB file is declared to be finished when it's
> >>> only just started. It looks like what's being measured is the
> >>> rate of handoff to network buffers. This machine has a quad-core
> >>> i7 CPU with 16GB of RAM and isn't doing much else, so the entire
> >>> file could be copied to system buffers very quickly. However the
> >>> actual LAN is 100Mbps so the real copy takes several minutes, and
> >>> it's only then that I get the pop-up saying it's finished.
> >>
> >> The UI can only indicate what is visible to user space, it has no
> >> way to, nor is it expected to, know what the kernel does behind
> >> the scenes. If the kernel reports that it has processed the data,
> >> the UI shows it as processed. That is exactly as designed.
> > 
> > No doubt, however it's not how it's *read*. The interface could be
> > clearer about what it's actually showing when the information is
> > misleading.
> 
> how should it?
> 
> if you write 100 MB to disk and the kernel buffers it
> from the application you are done, that's how any
> modern operating system works for decades

Well in that case the app should say that the data has been moved/copied
to a buffer, rather than to the destination.

A user might think that the data transfer is complete when in reality
it isn't, and this can potentially lead to data loss or corruption.
Suppose I wait for the interface to tell me that the file has been
copied, and then I immediately put my laptop to standby, and try to
access the NFS copy of the file from another machine. Data corruption
is guaranteed, because the laptop went into standby before the
transfer has actually completed.

The interface must not lie to the user about what information it is
reporting. It should not say "file copied 100%" when all it measures is
the transfer to the kernel's buffer.

Best, :-)
Marko