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

[Chris Friesen]

On 05/08/2014 09:40 AM, Chris Friesen wrote:
> On 05/08/2014 07:47 AM, Amit Shah wrote:
>
> > Chris, I just tried a simple test this way:
> >
> > ./x86_64-softmmu/qemu-system-x86_64 -device virtio-serial-pci -device
> > virtserialport -S -monitor stdio -nographic
> >
> > and it didn't crash for me.  This was with qemu.git.  Perhaps you can
> > try in a similar way.
>
> I just tried it with the "stable-1.4" branch from upstream with my first
> patch added on.

> Anyway, it seems to boot up okay, which is better than what I was
> getting before.


Turns out I spoke too soon.  With the patch applied, it boots, but if I 
try to do a live migration both the source and destination crash.  This 
happens for both the master branch as well as the stable-1.4 branch.

If I back out the patch, it works fine.  If I leave the patch in and 
disable kvm acceleration it works fine.


I'm running the source as

/tmp/qemu-system-x86_64-upstream  -machine accel=kvm -m 1000 
test-cgcs-guest.img -device virtio-serial -chardev 
socket,path=/tmp/foo,server,nowait,id=foo -device 
virtserialport,chardev=foo,name=myfoo -monitor stdio


and the dest as

/tmp/qemu-system-x86_64-upstream  -machine accel=kvm -m 1000 
test-cgcs-guest.img -device virtio-serial -chardev 
socket,path=/tmp/foo,server,nowait,id=foo -device 
virtserialport,chardev=foo,name=myfoo -monitor stdio -incoming tcp:0:4444


and I'm triggering the migration with

migrate -d tcp:localhost:4444



On the dest side monitor I get:

(qemu) qemu: warning: error while loading state section id 3
load of migration failed



I managed to get gdb working, but it's not very helpful.  With gdb 
attached to the destination process I just get:

[Thread 0x7f760f6dc700 (LWP 15328) exited]
[Inferior 1 (process 15326) exited normally]