[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] question about migration
Andrew Cooper writes ("Re: [Xen-devel] question about migration"): > On 04/01/16 15:31, Ian Jackson wrote: > > * It is not possible to resume the domain in the source after it has > > suspended. > > This functionality exists and is already used in several circumstances, > both by libxl, and other toolstacks. Oh! > xl has an added split-brain problem here that plain demonic toolstacks > don't have; specifically that there are two completely independent > processes playing with the domain state at the same time. > > The daemonic xl needs to ignore DOMAIN_SHUTDOWN and tidy up only after > DOMAIN_DEATH. Under these circumstances, a failed migrate which resumes > the domain won't result in qemu being cleaned up. I think there is some kind of further underlying problem here. Suppose a domain goes into SHUTDOWN with reason code SUSPEND. Then later it is resumed again (perhaps the migration failed). And later it shuts down cleanly. Will this generate a second @releaseDomain ? How is a toolstack supposed to discover this situation ? Should libxl simply treat domains in state SHUTDOWN/SUSPEND as if they were running, and not issue a notification to anyone ? > > * @releaseDomain does not have a specific domain which is the "subject > > of @releaseDomain". Arguably this is unhelpful, but it is not > > libxl's fault. It arises from the VIRQ generated by Xen. Note that > > xenstored needs to search its own list of active domains to see what > > has happened; it generates the @releaseDomain event and throws away > > the domid. > > The semantics of @releaseDomain are quite mad, but this is have it has > always been. Yes. > The current semantics are a scalability limitation which someone in > XenServer will likely get around to in due course (we support 1000 VMs > per host). Jolly good :-). Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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