Re: [Qemu-devel] [PATCH v8 0/3] Throttle-down guest to help with live migration convergence

[Peter Lieven]

Hi all,

is it possible that not v8 of this patch got merged?
Without checking line-by-line I see at least that this here

+# @auto-converge: If enabled, QEMU will automatically throttle down the guest
+#          to speed up convergence of RAM migration. (since 1.6)
+#

is missing in qapi-schema.json.

BR,
Peter



On 24.06.2013 11:49, Chegu Vinod wrote:
> Busy enterprise workloads hosted on large sized VM's tend to dirty
> memory faster than the transfer rate achieved via live guest migration.
> Despite some good recent improvements (& using dedicated 10Gig NICs
> between hosts) the live migration does NOT converge.
>
> If a user chooses to force convergence of their migration via a new
> migration capability "auto-converge" then this change will auto-detect
> lack of convergence scenario and trigger a slow down of the workload
> by explicitly disallowing the VCPUs from spending much time in the VM
> context.
>
> The migration thread tries to catchup and this eventually leads
> to convergence in some "deterministic" amount of time. Yes it does
> impact the performance of all the VCPUs but in my observation that
> lasts only for a short duration of time. i.e. end up entering
> stage 3 (downtime phase) soon after that. No external trigger is
> required.
>
> Thanks to Juan and Paolo for their useful suggestions.
>
> ---
> Changes from v7:
> - added a missing else to patch 3/3.
>
> Changes from v6:
> - incorporated feedback from Paolo.
> - rebased to latest qemu.git and removing RFC
>
> Changes from v5:
> - incorporated feedback from Paolo & Igor.
> - rebased to latest qemu.git
>
> Changes from v4:
> - incorporated feedback from Paolo.
> - split into 3 patches.
>
> Changes from v3:
> - incorporated feedback from Paolo and Eric
> - rebased to latest qemu.git
>
> Changes from v2:
> - incorporated feedback from Orit, Juan and Eric
> - stop the throttling thread at the start of stage 3
> - rebased to latest qemu.git
>
> Changes from v1:
> - rebased to latest qemu.git
> - added auto-converge capability(default off) - suggested by Anthony Liguori &
>                                                  Eric Blake.
>
> Signed-off-by: Chegu Vinod <address@hidden>
> ---
>
> Chegu Vinod (3):
>    Introduce async_run_on_cpu()
>    Add 'auto-converge' migration capability
>    Force auto-convegence of live migration
>
>   arch_init.c                   |   85 +++++++++++++++++++++++++++++++++++++++++
>   cpus.c                        |   29 ++++++++++++++
>   include/migration/migration.h |    2 +
>   include/qemu-common.h         |    1 +
>   include/qom/cpu.h             |   10 +++++
>   migration.c                   |    9 ++++
>   qapi-schema.json              |    5 ++-
>   7 files changed, 140 insertions(+), 1 deletions(-)