RE: [PATCH 0/6] Fast balloon & fast live migration

From: Li, Liang Z
Date: Thu Jun 23 2016 - 04:27:35 EST


Any comments?

Liang


> -----Original Message-----
> From: Li, Liang Z
> Sent: Monday, June 13, 2016 5:47 PM
> To: kvm@xxxxxxxxxxxxxxx
> Cc: virtio-dev@xxxxxxxxxxxxxxxxxxxx; qemu-devel@xxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; mst@xxxxxxxxxx; Li, Liang Z
> Subject: [PATCH 0/6] Fast balloon & fast live migration
>
> The implementation of the current virtio-balloon is not very efficient, bellow
> is test result of time spends on inflating the balloon to 3GB of a 4GB idle
> guest:
>
> a. allocating pages (6.5%, 103ms)
> b. sending PFNs to host (68.3%, 787ms)
> c. address translation (6.1%, 96ms)
> d. madvise (19%, 300ms)
>
> It takes about 1577ms for the whole inflating process to complete.
> The test shows that the bottle neck is the stage b and stage d.
>
> If using a bitmap to send the page info instead of the PFNs, we can reduce
> the overhead in stage b quite a lot. Furthermore, it's possible to do the
> address translation and the madvise with a bulk of pages, instead of the
> current page per page way, so the overhead of stage c and stage d can also
> be reduced a lot.
>
> In addition, we can speed up live migration by skipping process guest's free
> pages.
>
> Patch 1 and patch 2 are the kernel side implementation which are intended
> to speed up the inflating & deflating process by adding a new feature to the
> virtio-balloon device. And now, inflating the balloon to 3GB of a 4GB idle
> guest only takes 200ms, it's about 8 times as fast as before.
>
>
> Patch 3 and patch 4 add the cache drop support, now hypervisor can request
> the guest to drop it's cache. It's useful before inflating the virtio-balloon and
> before starting live migration.
>
> Patch 5 and patch 6 save guest's free page information into a page bitmap
> and send the bitmap to host through balloon's virt queue.
>
> Liang Li (6):
> virtio-balloon: rework deflate to add page to a list
> virtio-balloon: speed up inflate/deflate process
> mm:split the drop cache operation into a function
> virtio-balloon: add drop cache support
> mm: add the related functions to get free page info
> virtio-balloon: tell host vm's free page info
>
> drivers/virtio/virtio_balloon.c | 321
> +++++++++++++++++++++++++++++++-----
> fs/drop_caches.c | 22 ++-
> include/linux/mm.h | 1 +
> include/uapi/linux/virtio_balloon.h | 2 +
> mm/page_alloc.c | 40 +++++
> 5 files changed, 339 insertions(+), 47 deletions(-)
>
> --
> 1.9.1