Gerd Hoffmann <kra...@redhat.com> writes: > Hi, > >> > It would be nice for this series to evolve to a generic QMP jobs series >> > so that all background operations are visible to the client and a useful >> > subset of management primitives can be implemented on a per-command >> > basis. Both live migration and existing block jobs could use this code >> > so that we don't have multiple copies of the same infrastructure. >> >> Indeed, but I would need to know what proposal or requirements the >> block layer have here, and I would appreciate if they took time to >> review mine. > > Disclaimer: Havn't looked into the qmp (especially block jobs) details > too much. > > But I suspect we can have both, sharing most of the infrastructure, > without too much effort. > > We have block jobs today. Other areas in qemu can use that too. So > moving the jobs infrastructure from block to qmp level makes perfect > sense to me. Live migration and possibly others can start using it.
Yes. When everything uses a generic job infrastructure instead of rolling their own, things get simpler and more regular. Should take less code, too, although backward compatibility might thwart that to a degree. > And once we have that building async commands on top of that is probably > easy. It'll be just a primitive job which typically takes at most a few > seconds to finish, has no ->cancel() callback and sends a different kind > of completion notification ... Plausible. "Can" doesn't imply "should", of course. Here's my current thinking: * "Jobs" are a generalization of the ad hoc ways we do long-running activities, including "block jobs" and migration. Having one general way to do a common, non-trivial thing makes sense. * Block people have wanted "jobs" for quite a while. The limitations of the existing "block jobs" are getting painful. * Given this "jobs" concept, asynchronous commands are a degenerate case of it. Whether they are a common case, I can't say, yet. How the special case fits into the whole, and whether it's worth having needs to be evaluated. * Like Gerd, I think we should do jobs first.
