Am 22.04.2014 um 18:22 hat Max Reitz geschrieben: > On 22.04.2014 17:19, Eric Blake wrote: > >On 04/17/2014 03:59 PM, Max Reitz wrote: > >>After the top image has been committed into an image in its backing > >>chain, all images above that base image should be emptied to restore the > >>old qemu-img commit behavior. > >> > >>Signed-off-by: Max Reitz <mre...@redhat.com> > >>--- > >> qemu-img.c | 87 > >> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--- > >> 1 file changed, 84 insertions(+), 3 deletions(-) > >Does emptying an image take significant time? If so, does that need to > >be reflected in the progress meter? > > For a 16 GB image I have here (should be nearly full) it took 1:22 > min. Copying it took six minutes, so I guess committing it would > take even more. I think the ratio is small enough not to include it > in the progress meter.
Did you check why it took that long? Sounds like we're issuing a lot of independent discard requests instead of few big ones. Is the image heavily fragmented? > Furthermore, I don't see a reasonable implementation for a > make_empty progress output: As a general implementation for all > image formats implementing discard will not work (the qcow2 > implementation clearly states that discarded sectors should read > back as zero) We can always add new flags or a separate new callback if it improves things. Kevin
