On Sunday 20 November 2011 16:20:14 Darren Steven wrote:
It's caused by the kernel allocating large write buffers that can
represent
many minutes (or hours) of write time for a slow USB device. You copy that
file from a higher performing storage device, and you end up with many GB
buffered writes. KDE (or something in the UI render path) decides to stop
while doing an fsync ( I'm not sure exactly what), and you need to wait for
that to complete.
[snip]
It's probably a default Fedora may want to tweak based on machine
config,
and I understand there has been some healthy discussion in kernel lists
about it. To me it seems the kernel needs to become acutely aware of what
the real throughput of a device is, not what the device claims, and allow
the user to set minimum write latency. Almost like tcp's windowing system
(with slow start). Filesystems matter too apparently, and ext4 is renowned
for latency issues (btrfs more so)
Thanks for the explanation, it's very interesting. Can you post a link to the
thread (I guess on LKML) with that discussion?
Best, :-)
Marko