Hi, I'm experiencing guest freezes and top is showing 99% system time whenever I try to run more than one guest on my VM host. Please help me to make a decent bug report! libvirt: 1.2.1 qemu: 1.7.0 All individual VMs run perfectly on their own, only when two or more are started at the same time I see these problems. I've not idea how to find where the processes are getting "stuck". I've had this working in the past, with the only differences I'm aware of being version increments and that I previously used to use openvswitch, but switched to simple linux bridge after rebuilding the setup. If I strace for a few seconds on one of these processes which are sucking up CPU, all I see is, e.g.: [root@kvmhost1 ~]# strace -c -p 12392 Process 12392 attached ^CProcess 12392 detached % time seconds usecs/call calls errors syscall ------ ----------- ----------- --------- --------- ---------------- 0.00 0.000000 0 1 rt_sigpending 0.00 0.000000 0 1 1 rt_sigtimedwait ------ ----------- ----------- --------- --------- ---------------- 100.00 0.000000 2 1 total Any advice on what to do next appreciated! Kind Regards, Kevin Shanahan. -- example top output -- top - 12:03:42 up 22:15, 3 users, load average: 3.27, 2.21, 1.64 Threads: 112 total, 4 running, 108 sleeping, 0 stopped, 0 zombie %Cpu(s): 2.3 us, 97.7 sy, 0.0 ni, 0.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem: 8169596 total, 3119260 used, 5050336 free, 0 buffers KiB Swap: 0 total, 0 used, 0 free. 435704 cached Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 12392 root 20 0 2886636 138272 6380 R 59.2 1.7 3:19.38 qemu-system-x+ 11053 root 20 0 3473808 2.031g 6408 R 57.5 26.1 28:47.17 qemu-system-x+ 11054 root 20 0 3473808 2.031g 6408 R 36.9 26.1 19:29.52 qemu-system-x+ 12393 root 20 0 2886636 138272 6380 S 36.3 1.7 2:14.98 qemu-system-x+ 11051 root 20 0 3473808 2.031g 6408 S 7.7 26.1 8:11.11 qemu-system-x+ 11057 root 20 0 3473808 2.031g 6408 S 0.0 26.1 0:00.00 qemu-system-x+ 12342 root 20 0 1080460 173156 6312 S 0.0 2.1 0:02.44 qemu-system-x+ 12344 root 20 0 1080460 173156 6312 S 0.0 2.1 0:29.59 qemu-system-x+ 12346 root 20 0 1080460 173156 6312 S 0.0 2.1 0:00.00 qemu-system-x+ 12390 root 20 0 2886636 138272 6380 S 0.0 1.7 0:01.71 qemu-system-x+ 12396 root 20 0 2886636 138272 6380 S 0.0 1.7 0:00.00 qemu-system-x+ -- perf top output -- (seems pretty normal, I think?) Samples: 3M of event 'cycles', Event count (approx.): 62626938657 20.90% [kernel] [k] read_hpet ◆ 4.47% [kernel] [k] __schedule ▒ 3.75% [kernel] [k] update_cfs_shares ▒ 3.50% [kernel] [k] kvm_arch_vcpu_ioctl_run ▒ 3.03% [kernel] [k] native_read_tsc ▒ 2.42% [kernel] [k] update_curr ▒ 2.22% [kernel] [k] native_write_msr_safe ▒ -- virsh dumpxml win7 -- <domain type='kvm' id='4'> <name>win7</name> <uuid>fb683081-01c0-ee11-3e6f-580c62216b59</uuid> <memory unit='KiB'>2097152</memory> <currentMemory unit='KiB'>2097152</currentMemory> <vcpu placement='static'>2</vcpu> <resource> <partition>/machine</partition> </resource> <os> <type arch='x86_64' machine='pc-i440fx-1.7'>hvm</type> <boot dev='cdrom'/> <boot dev='hd'/> </os> <features> <acpi/> <apic/> <pae/> </features> <clock offset='localtime'/> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>restart</on_crash> <devices> <emulator>/usr/bin/qemu-system-x86_64</emulator> <disk type='volume' device='disk'> <driver name='qemu' type='raw' cache='none'/> <source pool='vmspace' volume='win7.img'/> <target dev='vda' bus='virtio'/> <alias name='virtio-disk0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/> </disk> <disk type='volume' device='cdrom'> <driver name='qemu' type='raw'/> <target dev='hdc' bus='ide'/> <readonly/> <alias name='ide0-1-0'/> <address type='drive' controller='0' bus='1' target='0' unit='0'/> </disk> <controller type='ide' index='0'> <alias name='ide0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/> </controller> <controller type='usb' index='0'> <alias name='usb0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/> </controller> <controller type='pci' index='0' model='pci-root'> <alias name='pci.0'/> </controller> <interface type='bridge'> <mac address='52:54:00:cd:7a:f1'/> <source bridge='br0'/> <target dev='vnet1'/> <model type='virtio'/> <alias name='net0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> <serial type='pty'> <source path='/dev/pts/2'/> <target port='0'/> <alias name='serial0'/> </serial> <console type='pty' tty='/dev/pts/2'> <source path='/dev/pts/2'/> <target type='serial' port='0'/> <alias name='serial0'/> </console> <input type='tablet' bus='usb'> <alias name='input0'/> </input> <input type='mouse' bus='ps2'/> <graphics type='vnc' port='5901' autoport='yes' listen='127.0.0.1'> <listen type='address' address='127.0.0.1'/> </graphics> <video> <model type='cirrus' vram='9216' heads='1'/> <alias name='video0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/> </video> <memballoon model='virtio'> <alias name='balloon0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/> </memballoon> </devices> <seclabel type='none'/> </domain> -- virsh dumpxml arch1 -- <domain type='kvm' id='6'> <name>arch1</name> <uuid>fe10ccad-c4f0-b1ac-5b5b-fab023bb1176</uuid> <memory unit='KiB'>1572864</memory> <currentMemory unit='KiB'>1572864</currentMemory> <vcpu placement='static'>2</vcpu> <resource> <partition>/machine</partition> </resource> <os> <type arch='x86_64' machine='pc-i440fx-1.7'>hvm</type> <boot dev='cdrom'/> <boot dev='hd'/> </os> <features> <acpi/> <apic/> <pae/> </features> <clock offset='utc'/> <on_poweroff>destroy</on_poweroff> <on_reboot>restart</on_reboot> <on_crash>restart</on_crash> <devices> <emulator>/usr/bin/qemu-system-x86_64</emulator> <disk type='volume' device='disk'> <driver name='qemu' type='raw' cache='none'/> <source pool='vmspace' volume='arch1.img'/> <target dev='vda' bus='virtio'/> <alias name='virtio-disk0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/> </disk> <disk type='block' device='cdrom'> <driver name='qemu' type='raw'/> <target dev='hdc' bus='ide'/> <readonly/> <alias name='ide0-1-0'/> <address type='drive' controller='0' bus='1' target='0' unit='0'/> </disk> <controller type='ide' index='0'> <alias name='ide0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/> </controller> <controller type='usb' index='0'> <alias name='usb0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/> </controller> <controller type='pci' index='0' model='pci-root'> <alias name='pci.0'/> </controller> <interface type='bridge'> <mac address='52:54:00:a8:d8:4e'/> <source bridge='br0'/> <target dev='vnet2'/> <model type='virtio'/> <alias name='net0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> </interface> <serial type='pty'> <source path='/dev/pts/5'/> <target port='0'/> <alias name='serial0'/> </serial> <console type='pty' tty='/dev/pts/5'> <source path='/dev/pts/5'/> <target type='serial' port='0'/> <alias name='serial0'/> </console> <input type='mouse' bus='ps2'/> <graphics type='vnc' port='5902' autoport='yes' listen='127.0.0.1'> <listen type='address' address='127.0.0.1'/> </graphics> <video> <model type='cirrus' vram='9216' heads='1'/> <alias name='video0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/> </video> <memballoon model='virtio'> <alias name='balloon0'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/> </memballoon> </devices> <seclabel type='none'/> </domain> -- virsh pool-dumpxml vmspace -- <pool type='netfs'> <name>vmspace</name> <uuid>29cd171a-5727-4881-b858-e6e2e118d56d</uuid> <capacity unit='bytes'>527373959168</capacity> <allocation unit='bytes'>114542247936</allocation> <available unit='bytes'>412831711232</available> <source> <host name='10.48.50.20'/> <dir path='/vmspace/images'/> <format type='nfs'/> </source> <target> <path>/srv/kvm/images</path> <permissions> <mode>0755</mode> <owner>-1</owner> <group>-1</group> </permissions> </target> </pool>