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Re: [Qemu-devel] [PATCH v12 1/6] migration: introduce postcopy-blocktime
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH v12 1/6] migration: introduce postcopy-blocktime capability |
Date: |
Tue, 2 Jan 2018 15:20:28 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 |
On 10/30/2017 08:16 AM, Alexey Perevalov wrote:
> Right now it could be used on destination side to
> enable vCPU blocktime calculation for postcopy live migration.
> vCPU blocktime - it's time since vCPU thread was put into
> interruptible sleep, till memory page was copied and thread awake.
>
> Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> Signed-off-by: Alexey Perevalov <address@hidden>
> ---
> migration/migration.c | 9 +++++++++
> migration/migration.h | 1 +
> qapi/migration.json | 6 +++++-
> 3 files changed, 15 insertions(+), 1 deletion(-)
>
Is there any reason this has to be a new capability rather than
unconditionally enabled? What are the trade-offs for enabling vs.
disabling the capability that warrant it being a knob? Can we do a
better job of documenting in which cases the user would want to change
the knob from its default value, if we even need it to be a knob?
> +++ b/qapi/migration.json
> @@ -352,12 +352,16 @@
> #
> # @x-multifd: Use more than one fd for migration (since 2.11)
> #
> +# @postcopy-blocktime: Calculate downtime for postcopy live migration
> +# (since 2.11)
> +#
> # Since: 1.2
> ##
> { 'enum': 'MigrationCapability',
> 'data': ['xbzrle', 'rdma-pin-all', 'auto-converge', 'zero-blocks',
> 'compress', 'events', 'postcopy-ram', 'x-colo', 'release-ram',
> - 'block', 'return-path', 'pause-before-switchover', 'x-multifd' ] }
> + 'block', 'return-path', 'pause-before-switchover', 'x-multifd',
> + 'postcopy-blocktime' ] }
>
> ##
> # @MigrationCapabilityStatus:
>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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