[RFC for qemu v4 0/2] virtio-balloon: Add option cont-pages to set VIRTIO_BALLOON_F_CONT_PAGES

[Hui Zhu <teawater@gmail.com>]

Code of current version for Linux and qemu is available in [1] and [2].
Update of this version:
1. Report continuous pages will increase the speed.  So added deflate
   continuous pages.
2. According to the comments from David in [3], added 2 new vqs icvq and
   dcvq to get continuous pages with format 32 bits pfn and 32 bits size.

Following is the introduction of the function.
Set option cont-pages to on will open flags VIRTIO_BALLOON_F_CONT_PAGES.
qemu will get continuous pages from icvq and dcvq and do madvise
MADV_WILLNEED and MADV_DONTNEED with the pages.
Opening this flag can bring two benefits:
1. Increase the speed of balloon inflate and deflate.
2. Decrease the splitted THPs number in the host.

[1] https://github.com/teawater/linux/tree/balloon_conts
[2] https://github.com/teawater/qemu/tree/balloon_conts
[3] https://lkml.org/lkml/2020/5/13/1211

Hui Zhu (2):
  virtio_balloon: Add cont-pages and icvq
  virtio_balloon: Add dcvq to deflate continuous pages

 hw/virtio/virtio-balloon.c                      |   92 +++++++++++++++---------
 include/hw/virtio/virtio-balloon.h              |    2
 include/standard-headers/linux/virtio_balloon.h |    1
 3 files changed, 63 insertions(+), 32 deletions(-)