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Re: [Qemu-devel] virtio-serial-pci very expensive during live migration

From: Chris Friesen
Subject: Re: [Qemu-devel] virtio-serial-pci very expensive during live migration
Date: Thu, 8 May 2014 14:57:01 -0600
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0

On 05/08/2014 10:02 AM, Paolo Bonzini wrote:
Il 08/05/2014 17:57, Chris Friesen ha scritto:

The fact remains that qemu crashes when I apply the patch.  I also
patching it as below in virtio_pci_vmstate_change().  That would allow
the VM to boot, but it would crash when I tried to do a live migration.

Can you give us your command line and a backtrace?

For the backtrace, you mean with a core file?  Or is there a better way?

You can attach gdb to the qemu process, and run "thread apply all bt"
when QEMU crashes.

For the commandline, it's coming from OpenStack via libvirt, so it's fairly complicated:

/usr/bin/kvm -c 0x00000000000000000000000000000001 -n 4 --proc-type=secondary --file-prefix=vs -- -enable-dpdk -name instance-00000007 -S -machine pc-i440fx-1.4,accel=kvm,usb=off -m 512 -mem-prealloc -mem-path /mnt/huge-2048kB/libvirt/qemu -smp 2,sockets=2,cores=1,threads=1 -uuid b277d785-9c31-45be-91d3-15b7b1aca974 -smbios type=1,manufacturer=OpenStack Foundation,product=OpenStack Nova,version=2013.2.2,serial=00000000-0000-3848-3342-4e5037313536,uuid=b277d785-9c31-45be-91d3-15b7b1aca974 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/instance-00000007.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=utc,driftfix=slew -no-kvm-pit-reinjection -no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x3 -drive file=/etc/nova/instances/b277d785-9c31-45be-91d3-15b7b1aca974/disk,if=none,id=drive-virtio-disk0,format=qcow2,cache=none -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -chardev file,id=charserial0,path=/etc/nova/instances/b277d785-9c31-45be-91d3-15b7b1aca974/console.log -device isa-serial,chardev=charserial0,id=serial0 -chardev pty,id=charserial1 -device isa-serial,chardev=charserial1,id=serial1 -chardev socket,id=charchannel0,path=/var/lib/libvirt/qemu/cgcs.heartbeat.instance-00000007.sock,server,nowait -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=cgcs.heartbeat -device usb-tablet,id=input0 -vnc -k en-us -vga cirrus -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x5 -device avp,port=4a05cedd-3868-449a-9728-899bbea10863,id=avp4a05cedd-38

As for the backtrace, I can attach gdb to the qemu process, but when I hit "c" to continue it gives an error:

Reading symbols from /lib64/libnss_files.so.2...(no debugging symbols found)...done.
Loaded symbols for /lib64/libnss_files.so.2

warning: File "/lib64/libthread_db-1.0.so" auto-loading has been declined by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".

warning: Unable to find libthread_db matching inferior's thread library, thread debugging will not be available.
0x00007f56c6366d23 in select () from /lib64/libc.so.6
(gdb) c
Cannot insert breakpoint -1.
Error accessing memory address 0x2f7c50: Input/output error.


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