Antoine Martin wrote: > On 02/27/2010 12:38 AM, Antoine Martin wrote: > >>> 1 0 0 98 0 1| 0 0 | 66B 354B| 0 0 | 30 11 > >>> 1 1 0 98 0 0| 0 0 | 66B 354B| 0 0 | 29 11 > >>>From that point onwards, nothing will happen. > >>>The host has disk IO to spare... So what is it waiting for?? > >>Moved to an AMD64 host. No effect. > >>Disabled swap before running the test. No effect. > >>Moved the guest to a fully up-to-date FC12 server > >>(2.6.31.6-145.fc12.x86_64), no effect. > >I have narrowed it down to the guest's filesystem used for backing > >the disk image which is loop mounted: although it was not > >completely full (and had enough inodes), freeing some space on it > >prevents the system from misbehaving. > > > >FYI: the disk image was clean and was fscked before each test. kvm > >had been updated to 0.12.3 > >The weird thing is that the same filesystem works fine (no system > >hang) if used directly from the host, it is only misbehaving via > >kvm... > > > >So I am not dismissing the possibility that kvm may be at least > >partly to blame, or that it is exposing a filesystem bug (race?) > >not normally encountered. > >(I have backed up the full 32GB virtual disk in case someone > >suggests further investigation) > Well, well. I've just hit the exact same bug on another *host* (not > a guest), running stock Fedora 12. > So this isn't a kvm bug after all. Definitely a loop+ext(4?) bug. > Looks like you need a pretty big loop mounted partition to trigger > it. (bigger than available ram?) > > This is what triggered it on a quad amd system with 8Gb of ram, > software raid-1 partition: > mount -o loop 2GB.dd source > dd if=/dev/zero of=8GB.dd bs=1048576 count=8192 > mkfs.ext4 -f 8GB.dd > mount -o loop 8GB.dd dest > rsync -rplogtD source/* dest/ > umount source > umount dest > ^ this is where it hangs, I then tried to issue a 'sync' from > another terminal, which also hung. > It took more than 10 minutes to settle itself, during that time one > CPU was stuck in wait state. This sounds like: https://bugzilla.kernel.org/show_bug.cgi?id=15906 https://bugzilla.redhat.com/show_bug.cgi?id=588930 -jim -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
