Daniel P. Berrangé <berra...@redhat.com> writes:
> On Fri, Jan 14, 2022 at 12:22:13PM +0100, Markus Armbruster wrote:
>> Nikita Lapshin <nikita.laps...@virtuozzo.com> writes:
>>
>> > If this capability is enabled migration stream
>> > will have RAM section only.
>> >
>> > Signed-off-by: Nikita Lapshin <nikita.laps...@virtuozzo.com>
>>
>> [...]
>>
>> > diff --git a/qapi/migration.json b/qapi/migration.json
>> > index d53956852c..626fc59d14 100644
>> > --- a/qapi/migration.json
>> > +++ b/qapi/migration.json
>> > @@ -454,6 +454,8 @@
>> > #
>> > # @no-ram: If enabled, migration stream won't contain any ram in it.
>> > (since 7.0)
>> > #
>> > +# @ram-only: If enabled, only RAM sections will be sent. (since 7.0)
>> > +#
>>
>> What happens when I ask for 'no-ram': true, 'ram-only': true?
>
> So IIUC
>
> no-ram=false, ram-only=false => RAM + vmstate
> no-ram=true, ram-only=false => vmstate
> no-ram=false, ram-only=true => RAM
> no-ram=true, ram-only=true => nothing to send ?
>
> I find that the fact that one flag is a negative request and
> the other flag is a positive request to be confusing.
Me too.
> If we must have two flags then could we at least use the same
> style for both. ie either
>
> @no-ram
> @no-vmstate
>
> Or
>
> @ram-only
> @vmstate-only
I strongly prefer "positive" names for booleans, avoiding double
negation.
> Since the code enforces these flags are mutually exclusive
> though, it might point towards being handled by a enum
>
> { 'enum': 'MigrationStreamContent',
> 'data': ['both', 'ram', 'vmstate'] }
Enumerating the combinations that are actually valid is often nicer than
a set of flags that look independent, but aren't.
MigrationCapability can only do flags. For an enum, we'd have to use
MigrationParameters & friends. For an example, check out
@multifd-compression there.
> none of these approaches are especially future proof if we ever
> need fine grained control over sending a sub-set of the non-RAM
> vmstate. Not sure if that matters in the end.
>
>
> Regards,
> Daniel
