Re: [Qemu-devel] [PATCH 0/3] Live migration without shared storage (improved version)

[Liran Schour]

address@hidden wrote on 10/09/2009
17:35:53:

> On 10 sept. 2009, at 12:26, address@hidden wrote:
>
> > This series adds support for live migration without shared storage,
> > means
> > copy the storage while migrating. It was tested with KVM. Supports 2
> > ways
> > to replicate the storage during migration:
> > 1. Complete copy of storage to destination
> > 2. Assuming the storage is cow based, copy only the allocated
> >    data, time of the migration will be linear with the amount of
> > allocated
> >    data (user responsibility to verify that the same backend file
> > reside
> >    on src and destination).
> >
> > Live migration will work as follows:
> > (qemu) migrate -d tcp:0:4444 # for ordinary live migration
> > (qemu) migrate -d blk tcp:0:4444 # for live migration with complete
> > storage copy
> > (qemu) migrate -d blk inc tcp:0:4444 # for live migration with
> > incremental storage copy, storage is cow based.
> >
> > The patches are against
git://git.kernel.org/pub/scm/virt/kvm/qemu-kvm.git
> > kvm-87
> >
> >
> >
>
>
> Just tried with the v2 of the third patch. Now throughput is much
> better when the disk image has already been allocated (zero'd with dd)
> on the receiving end.
>
> However, you must have a memory leak somewhere: at the end of the
> migration of a 128MB VM, the destination machine was swapping and qemu
> was using nearly 2GB of resident memory (the size of the disk image
> was 2GB).

It seems that there is a memory leak but from what I see it is a memory
leak in
raw_aio_writev. Seems like bdrv_aio_writev does not call the callback on
completion.
Therefore the buffer allocated for the aio_writev is not being freed.
Anyone knows
about this bug?

- Liran