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Re: [Qemu-devel] [PATCH v2 0/3] migration capability to discard the migr

From: Pavel Butsykin
Subject: Re: [Qemu-devel] [PATCH v2 0/3] migration capability to discard the migrated ram pages
Date: Fri, 3 Mar 2017 11:39:50 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0

On 14.02.2017 17:02, Dr. David Alan Gilbert wrote:
Hi Pavel,
   I was curious, having merged this, how you're using postcopy; do you switch
into postcopy mode immediately or wait until the first sync or what?
Do you find yourself in postcopy mode long enough that it's worth
doing the release?  If so on what size VMs are you working with?


Hi Dave,
I'm sorry it took so long, I was on vacation. And thanks for the quick
review and merge!

We want to use this function to update Qemu without rebooting VMs. It
looks like a local migration on the same host. Now, switching into
postcopy mode is done immediately, the size of VMs can be very

* Pavel Butsykin (address@hidden) wrote:
This feature frees the migrated memory on the source during postcopy-ram
migration. In the second step of postcopy-ram migration when the source vm
is put on pause we can free unnecessary memory. It will allow, in particular,
to start relaxing the memory stress on the source host in a load-balancing

Changes from v1:
- changed name of the interfaces (discard to release)
- fix make check error
- add more comments to qemu_iovec_release_ram()
- rebase on "Postcopy: Hugepage support" (David's patch series)
- removed ram_discard_page for xbzrle
- fix erroneous release memory in complete precopy (tie release-ram to postcopy)

Pavel Butsykin (3):
   migration: add MigrationState arg for ram_save_/compressed_/page()
   add 'release-ram' migrate capability
   migration: discard non-dirty ram pages after the start of postcopy

  include/migration/migration.h |  2 ++
  include/migration/qemu-file.h |  3 ++-
  migration/migration.c         | 13 ++++++++++
  migration/qemu-file.c         | 59 ++++++++++++++++++++++++++++++++++++++-----
  migration/ram.c               | 56 ++++++++++++++++++++++++++++++++++------
  qapi-schema.json              |  5 +++-
  6 files changed, 121 insertions(+), 17 deletions(-)


Dr. David Alan Gilbert / address@hidden / Manchester, UK

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