Re: [Qemu-devel] [PATCH qemu v3 0/6] Fast (de)inflating & fast live migration

[Michael S. Tsirkin]

On Fri, Oct 21, 2016 at 02:48:18PM +0800, Liang Li wrote:
> This patch set intends to do two optimizations, one is to speed up
> the (de)inflating process of virtio balloon, and another one which
> is to speed up the live migration process. We put them together
> because both of them are required to change the virtio balloon spec.
>  
> The main idea of speeding up the (de)inflating process is to use
> bitmap to send the page information to host instead of the PFNs, to
> reduce the overhead of virtio data transmission, address translation
> and madvise(). This can help to improve the performance by about 85%.
>  
> The idea of speeding up live migration is to skip process guest's
> free pages in the first round of data copy, to reduce needless
> data processing, this can help to save quite a lot of CPU cycles and
> network bandwidth. We get guest's free page information through the
> virt queue of virtio-balloon, and filter out these free pages during
> live migration. For an idle 8GB guest, this can help to shorten the
> total live migration time from 2Sec to about 500ms in the 10Gbps
> network environment.

So it looks like the host/guest interface here is still in flux,
I think it's best to defer this to QEMU 2.9.

If you think otherwise, pls let me know.


> Changes from v2 to v3:
>     * Merged two patches for kernel head file updating into one 
>     * Removed one patch which was unrelated with this feature 
>     * Removed the patch to migrate the vq elem, use a new way instead
> 
> Changes from v1 to v2:
>     * Abandon the patch for dropping page cache.
>     * Get a struct from vq instead of separate variables.
>     * Use two separate APIs to request free pages and query the status.
>     * Changed the virtio balloon interface.
>     * Addressed some of the comments of v1.
> 
> Liang Li (6):
>   virtio-balloon: update linux head file
>   virtio-balloon: speed up inflating & deflating process
>   balloon: get free page info from guest
>   bitmap: Add a new bitmap_move function
>   kvm: Add two new arch specific functions
>   migration: skip free pages during live migration
> 
>  balloon.c                                       |  47 +++-
>  hw/virtio/virtio-balloon.c                      | 273 
> ++++++++++++++++++++++--
>  include/hw/virtio/virtio-balloon.h              |  18 +-
>  include/qemu/bitmap.h                           |  13 ++
>  include/standard-headers/linux/virtio_balloon.h |  41 ++++
>  include/sysemu/balloon.h                        |  18 +-
>  include/sysemu/kvm.h                            |  18 ++
>  migration/ram.c                                 |  86 ++++++++
>  target-arm/kvm.c                                |  14 ++
>  target-i386/kvm.c                               |  37 ++++
>  target-mips/kvm.c                               |  14 ++
>  target-ppc/kvm.c                                |  14 ++
>  target-s390x/kvm.c                              |  14 ++
>  13 files changed, 581 insertions(+), 26 deletions(-)
> 
> -- 
> 1.8.3.1