[Qemu-devel] [PATCH kernel 0/2] speed up live migration by skipping free pages

[Liang Li <liang.z.li@intel.com>]

Current QEMU live migration implementation mark all guest's RAM pages
as dirtied in the ram bulk stage, all these pages will be processed
and it consumes quite a lot of CPU cycles and network bandwidth.

>From guest's point of view, it doesn't care about the content in free
page. We can make use of this fact and skip processing the free
pages, this can save a lot CPU cycles and reduce the network traffic
significantly while speed up the live migration process obviously.

This patch set is the kernel side implementation.

The virtio-balloon driver is extended to send the free page bitmap
from guest to QEMU.

After getting the free page bitmap, QEMU can use it to filter out
guest's free pages. This make the live migration process much more
efficient.

In order to skip more free pages, we add an interface to let the user
decide whether dropping the cache in guest during live migration.

Liang Li (2):
  mm: add the related functions to build the free page bitmap
  virtio-balloon: extend balloon driver to support the new feature

 drivers/virtio/virtio_balloon.c     | 100 ++++++++++++++++++++++++++++++++++--
 fs/drop_caches.c                    |  22 +++++---
 include/linux/fs.h                  |   1 +
 include/uapi/linux/virtio_balloon.h |   1 +
 mm/page_alloc.c                     |  46 +++++++++++++++++
 5 files changed, 157 insertions(+), 13 deletions(-)

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1.8.3.1