Re: [Qemu-devel] [PATCH v12 6/6] migration: add postcopy total blocktime into query-migrate

[Alexey Perevalov]

On 01/03/2018 12:26 AM, Eric Blake wrote:
> On 10/30/2017 08:16 AM, Alexey Perevalov wrote:
> > Postcopy total blocktime is available on destination side only.
> > But query-migrate was possible only for source. This patch
> > adds ability to call query-migrate on destination.
> > To be able to see postcopy blocktime, need to request postcopy-blocktime
> > capability.
> Why not display the stats unconditionally when they are available,
> instead of having to set a capability knob to request them?
That knob necessary to avoid regression if this information
is not necessary, we decided during so long discussion in previous
version of the patch set - it's not necessary always.
But if user requested blocktime and host can't calculate it,
e.g. due to appropriate feature isn't supported in host kernel,
yes, the value will be 0.

> > The query-migrate command will show following sample result:
> > {"return":
> >      "postcopy-vcpu-blocktime": [115, 100],
> >      "status": "completed",
> >      "postcopy-blocktime": 100
> > }}
> >
> > postcopy_vcpu_blocktime contains list, where the first item is the first
> > vCPU in QEMU.
> >
> > This patch has a drawback, it combines states of incoming and
> > outgoing migration. Ongoing migration state will overwrite incoming
> > state. Looks like better to separate query-migrate for incoming and
> > outgoing migration or add parameter to indicate type of migration.
> >
> > Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> > Signed-off-by: Alexey Perevalov <address@hidden>
> > ---
> > +++ b/qapi/migration.json
> > @@ -156,6 +156,13 @@
> >   #              @status is 'failed'. Clients should not attempt to parse the
> >   #              error strings. (Since 2.7)
> >   #
> > +# @postcopy-blocktime: total time when all vCPU were blocked during postcopy
> > +#           live migration (Since 2.11)
> 2.12 now.
>
> Should this mention the capability knob needed to enable this stat (or
> else get rid of the capability knob and always expose this when possible)?
>
> > +#
> > +# @postcopy-vcpu-blocktime: list of the postcopy blocktime per vCPU (Since 
> > 2.11)
> Also 2.12.
>
> > +#
> > +
> > +#
> >   # Since: 0.14.0
> >   ##
> >   { 'struct': 'MigrationInfo',
> > @@ -167,7 +174,9 @@
> >              '*downtime': 'int',
> >              '*setup-time': 'int',
> >              '*cpu-throttle-percentage': 'int',
> > -           '*error-desc': 'str'} }
> > +           '*error-desc': 'str',
> > +           '*postcopy-blocktime' : 'int64',
> > +           '*postcopy-vcpu-blocktime': ['int64']} }
> >   
> >   ##
> >   # @query-migrate:

--
Best regards,
Alexey Perevalov