Re: [Qemu-devel] [RFC PATCH v2 10/12] mc: expose tunable parameter for checkpointing frequency

["Michael R. Hines" <mrhines@linux.vnet.ibm.com>]

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On 04/04/2014 10:56 PM, Eric Blake wrote:
> On 04/03/2014 11:29 PM, Michael R. Hines wrote:
>>> I'm trying to thing of a back-compat method, which exploits the fact
>>> that we now have flat unions (something we didn't have when
>>> migrate-set-capabilities was first added).  Maybe something like:
>>>
>>> { 'type': 'MigrationCapabilityBase',
>>>     'data': { 'capability': 'MigrationCapability' } }
>>> { 'type': 'MigrationCapabilityBool',
>>>     'data': { 'state': 'bool' } }
>>> { 'type': 'Migration CapabilityInt',
>>>     'data': { 'value': 'int' } }
>>> { 'union': 'MigrationCapabilityStatus',
>>>     'base': 'MigrationCapabilityBase',
>>>     'discriminator': 'capability',
>>>     'data': {
>>>       'xbzrle': 'MigrationCapabilityBool',
>>>       'auto-converge': 'MigrationCapabilityBool',
>>> ...
>>>       'mc-delay': 'MigrationCapabilityInt'
>>>     } }
>>>
>>> along with a tweak to query-migrate-capabilities for full back-compat:
>>>
>>> # @query-migrate-capabilities
>>> # @extended: #optional defaults to false; set to true to see non-boolean
>>> capabilities (since 2.1)
>>> { 'command: 'query-migrate-capabilities',
>>>     'data': { '*extended': 'bool' },
>>>     'returns': ['MigrationCapabilityStatus'] }
>>>
>> I like this a lot - it's very complicated, but it is clean, I think.
> Good - that means I made sense in trying to explain it.  And the more I
> re-read my mail, the more I like the idea - fewer new commands, and make
> the existing commands both more powerful and more easily extensible, all
> while still being discoverable by libvirt without waiting for full
> schema introspection.

Alright, I've saved this proposal on the wiki on the MicroCheckpointing
TODO section:

http://wiki.qemu.org/Features/MicroCheckpointing#TODO

For now, I've got several other issues to address before "someone"
gets around to this (I'd assume the maintainer or someone else would
want to test the 'extended' feature by itself in isolation with the existing
set of migration commands before someone else like me attempts to
use it or start adding new features to it.)

- Michael


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