Hello,
After upgrading my KVM environment from Fedora 20 to Fedora 21 up2date
(hosts and guests, Intel CPU) I've the following problem:
1.) On the database VM PostgresSQL e.g. 2 processes hang with 100% cpu
2.) On the monitoring VM Munin/RRDtool also hangs with 100% cpu
Killing of processes is not possible, only reboot helps.
But I nailed it down to the following:
yum install strace
strace -y -p339
Process 339 attached
# no system calls here
^CProcess 339 detached
Going deeper:
yum --enablerepo fedora-debuginfo,updates-debuginfo install gdb
postgresql-debuginfo
gdb postgres 339
(gdb) bt
#0 0x00007fffffbf8ff8 in gettimeofday ()
#1 0x00000000006d425e in GetCurrentTimestamp () at timestamp.c:1274
(gdb) frame 1
#1 0x00000000006d425e in GetCurrentTimestamp () at timestamp.c:1274
1274 gettimeofday(&tp, NULL);
(same on second process here)
Quitting and reattaching gdb also hangs here, so gettimeofday takes 100%
CPU and never ends!
Therefore I guess this is a problem either in the Linux kernel or in
QEMU/KVM.
It might be the case that something changed in timer handling or some
default changed here. VMs are time syncrhonized with NTP so this might
also be a problem that the syscall hangs here.
Workaround when it happens: reboot ....
Any further ideas?
Thank you.
Ciao,
Gerhard