On Mon, Oct 10, 2011 at 10:08:26AM +0100, Daniel P. Berrange wrote: > On Mon, Oct 10, 2011 at 10:21:02AM +0800, Wen Congyang wrote: > > At 10/09/2011 06:23 PM, Richard W.M. Jones Write: > > > On Sun, Oct 09, 2011 at 10:49:57AM +0200, Jan Kiszka wrote: > > >> As explained in the other replies: It is way more future-proof to use an > > >> interface for this which was designed for it (remote gdb) instead of > > >> artificially relaxing reasonable constraints of the migration mechanism > > >> plus having to follow that format with the post-processing tool. > > > > > > Any interface that isn't "get this information off my production > > > server *now*" so that I can get the server restarted, and send it to > > > an expert to analyse -- is a poor interface, whether it was designed > > > like that or not. Perhaps we don't have the right interface at all, > > > but remote gdb is not it. > > > > What about the following idea? > > > > Introduce a new monitor command named dump, and this command accepts a > > filename. > > We can use almost all migration's code. We use this command to dump guest's > > memory, so there is no need to check whether the guest has a unmigratable > > device. > > I think it would be a good idea of QEMU had a dedicated 'dump' command > for this purpose, even if it was just an alias for 'migrate' initially. > I have never really liked the fact that we abuse the 'migrate' command > to generate a core dump. The resulting data file from this is more > complex than it really needs to be, causing complexity for post-processing > it. The needs of migration, are not entirely aligned with the needs of > core dumping in the long term, so we should allow the possibility of > their impls diverging without impacting apps using them. > > So adding a 'dump' command which wrote out data in a format that was > optimized for offline processing by tools like 'crash' (or the windows > equivalent) would be a good improvement, even if it just reuses the > migrate code for now.
The other reason why it would be good, is that we would then have a clearly defined standard "QEMU dump format", instead of "libvirt dump format for QEMU" Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|