On Mon, May 09, 2016 at 06:20:22PM +0200, Petr Tesarik wrote: > On Mon, 9 May 2016 17:13:07 +0100 > "Daniel P. Berrange" <berra...@redhat.com> wrote: > > > On Mon, May 09, 2016 at 09:52:28AM -0600, Eric Blake wrote: > > > On 05/07/2016 05:32 PM, Nan Li wrote: > > > > When running the command "dump-guest-memory", we usually need a large > > > > space > > > > of storage to save the dumpfile into disk. It costs not only much time > > > > to > > > > save a file in some of hard disks, but also costs limited storage in > > > > host. > > > > In order to reduce the saving time and make it convenient for users to > > > > dump > > > > the guest memory, we introduce a Filesystem in Userspace (FUSE) to save > > > > the > > > > dump file in RAM. It is selectable in the configure file, adding a > > > > compiling > > > > of package "fuse-devel". It doesn't change the way of dumping guest > > > > memory. > > > > > > Why introduce FUSE? Can we reuse NBD instead? > > > > The commit message talks of letting QEMU dump to RAM avoiding disk I/O. > > IOW, it seems like it could just dump to any tmpfs directory. > > > > I'm not really seeing a compelling reason why QEMU needs to mount a fuse > > filesystem itself - whatever app is using QEMU could handle mounting of > > fs without QEMU's involvement at all. > > The ultimate goal is to export internal QEMU state (memory content, > register values) as an ELF file, so you could simply reuse any existing > tools that can work with ELF dump files (gdb, crash, makedumpfile, > readelf, etc.) instead of re-inventing the wheel for each of those > tools. > > This cannot be really done from outside of QEMU without too much > overhead (how would you access guest memory from outside QEMU?).
Maybe I'm missing something, but IIUC the 'dump-guest-memory' monitor command in QEMU already dumps in ELF format which can be used by standard ELF tools. If you don't want that dump to hit disk, then you could mount a tmpfs and then tell QEMU to write to that. 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 :|
