Re: [libvirt] [PATCH v2 1/8] Added public API to enable post-copy migration

On 2014-09-30 17:16, Daniel P. Berrange wrote: > On Tue, Sep 30, 2014 at 05:11:03PM +0200, Jiri Denemark wrote: >> On Tue, Sep 30, 2014 at 16:39:22 +0200, Cristian Klein wrote: >>> Signed-off-by: Cristian Klein <cristian.klein(a)cs.umu.se&gt; >>> --- >>> include/libvirt/libvirt.h.in | 1 + >>> src/libvirt.c | 7 +++++++ >>> 2 files changed, 8 insertions(+) >>> >>> diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in >>> index 5217ab3..82f3aeb 100644 >>> --- a/include/libvirt/libvirt.h.in >>> +++ b/include/libvirt/libvirt.h.in >>> @@ -1225,6 +1225,7 @@ typedef enum { >>> VIR_MIGRATE_ABORT_ON_ERROR = (1 << 12), /* abort migration on I/O errors happened during migration */ >>> VIR_MIGRATE_AUTO_CONVERGE = (1 << 13), /* force convergence */ >>> VIR_MIGRATE_RDMA_PIN_ALL = (1 << 14), /* RDMA memory pinning */ >>> + VIR_MIGRATE_POSTCOPY = (1 << 15), /* enable (but don't start) post-copy */ >>> } virDomainMigrateFlags; >> >> I still think we should add an extra flag to start post copy >> immediately. To address your concerns about it, I don't think it's >> implementing a policy in libvirt. It's for apps that want to make sure >> migration converges without having to spawn another thread and monitor >> the progress or wait for a timeout. It's a bit similar to migrating a >> paused domain vs. migrating a running domain and pausing it when it >> doesn't seem to converge. > > Your point about spawning another thread makes me wonder if we should > actually look at adding a 'VIR_MIGRATE_ASYNC' method (that would require > P2P migration of course). If this flag were set, virDomainMigrateXXX would > only block for long enough to start the migration and then return. > > Callers can use the job info API to monitor progress & success/failure. > > Then we wouldn't have to keep adding flags like you suggest - apps can > just easily call the appropriate API right away with no threads needed This would make a lot of sense. The user would call: """ virDomainMigrateXXX(..., VIR_MIGRATE_POSTCOPY | VIR_MIGRATE_ASYNC) virDomainMigrateStartPostCopy(...) """ Would this be seen as more cumbersome than having a dedicated VIR_MIGRATE_POSTCOPY_AUTOSTART?