On Mon, Oct 10, 2011 at 11:34:44AM +0200, Jan Kiszka wrote: > On 2011-10-10 11:10, Daniel P. Berrange wrote: > > 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" > > A core file would be that format - for direct gdb processing. No > proprietary re-inventions please.
I have no personal attachment to any particular format, so if the standard core file format is possible, then we should definitely try to use it in QEMU. 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 :|
