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[Tim Gardner <tim.gardner@xxxxxxxxxxxxx>]

** Also affects: linux (Ubuntu Yakkety)
   Importance: Undecided
       Status: Incomplete

** Also affects: linux (Ubuntu Xenial)
   Importance: Undecided
       Status: New

** Changed in: linux (Ubuntu Yakkety)
       Status: Incomplete => Fix Committed

** Changed in: linux (Ubuntu Xenial)
       Status: New => In Progress

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https://bugs.launchpad.net/bugs/1587091

Title:
  Extended statistics from balloon for proper memory management

Status in linux package in Ubuntu:
  Fix Committed
Status in linux source package in Xenial:
  In Progress
Status in linux source package in Yakkety:
  Fix Committed

Bug description:
  There is QEMU/KVM and a Linux OS running inside the guest. 
  Inside the Linux guest a balloon consumes memory in accordance with 
  commands performed on the host side in QEMU and reports some statistics through memstat structure.
  For the Linux guest reported “free” value doesn’t describe the guest memory pressure at all.
  The provided patch set in Linux kernel extends the stat with available field.

  The problem is addressed in mainstream Linux with the following
  patchset:

  commit
  5057dcd0f1aaad57e07e728ba20a99e205c6b9de
  Author: Igor Redko <redkoi@xxxxxxxxxxxxx>
  Date: Thu Mar 17 15:09:34 2016 -0700
  virtio_balloon: export 'available' memory to balloon statistics

  Add a new field, VIRTIO_BALLOON_S_AVAIL, to virtio_balloon memory
  statistics protocol, corresponding to 'Available' in /proc/meminfo.

  It indicates to the hypervisor how big the balloon can be inflated
  without pushing the guest system to swap.

  Signed-off-by: Igor Redko <redkoi@xxxxxxxxxxxxx>
  Signed-off-by: Denis V. Lunev <den@xxxxxxxxxx>
  Reviewed-by: Roman Kagan <rkagan@xxxxxxxxxxxxx>
  Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
  Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
  Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

  
  commit d02bd27bd33dd7e8d22594cd568b81be0cb584cd
  Author: Igor Redko <redkoi@xxxxxxxxxxxxx>
  Date: Thu Mar 17 15:09:34 2016 -0700
  mm/page_alloc.c: calculate 'available' memory in a separate function

  Add a new field, VIRTIO_BALLOON_S_AVAIL, to virtio_balloon memory
  statistics protocol, corresponding to 'Available' in /proc/meminfo.

  It indicates to the hypervisor how big the balloon can be inflated
  without pushing the guest system to swap.  This metric would be very
  useful in VM orchestration software to improve memory management of
  different VMs under overcommit.

  This patch (of 2):

  Factor out calculation of the available memory counter into a separate
  exportable function, in order to be able to use it in other parts of the
  kernel.

  In particular, it appears a relevant metric to report to the hypervisor
  via virtio-balloon statistics interface (in a followup patch).

  Signed-off-by: Igor Redko <redkoi@xxxxxxxxxxxxx>
  Signed-off-by: Denis V. Lunev <den@xxxxxxxxxx>
  Reviewed-by: Roman Kagan <rkagan@xxxxxxxxxxxxx>
  Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
  Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
  Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

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