Behaviour of system tray bandwidth indicator

[Patrick O'Callaghan]

On Thu, 2014-03-20 at 13:14 +0100, Reindl Harald 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
> 
> if you don't want that behavior disable any caches and
> buffers but then your machine will be as slow as hardware
> years ago

Then why does the pop-up show "copy completed" only after it has been
transferred to the server? This is not consistent. In fact the more I
think about it the more wrong it seems. I'm being told by the widget
that X GB were sent in a fraction of a second (open to interpretation),
that the copy is not currently consuming any bandwidth (false), but that
it hasn't actually finished yet (true).

poc