Re: [PATCH 0/5] migration: Downtime observability improvements

[Peter Xu]

On Tue, Sep 26, 2023 at 05:18:36PM +0100, Joao Martins wrote:
> For now, mainly precopy data, and here I added both tracepoints and
> QMP stats via query-migrate. Postcopy is still missing.

IIUC many of those will cover postcopy too, but not all?

I think the problem is postcopy didn't update downtime_start, however it
updates MigrationState.downtime, and probably we can start to keep it more
like precopy, e.g., in postcopy_start(), where downtime_start can be
time_at_stop (or it can be more accurate; now it's probably fetching the
timestamp too early).

Basically if we want to expose anything, especially some qapi object, IMHO
we'd better make it work for both pre/post copy because otherwise it'll be
hard for mgmt app to know which qemu supports precopy only, and which
support both (if we'll add that for postcopy too).

Thanks,

-- 
Peter Xu