[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] reliable live migration of large and busy guests
> From: George Dunlap [mailto:George.Dunlap@xxxxxxxxxxxxx] > Subject: Re: [Xen-devel] reliable live migration of large and busy guests > > On Wed, Nov 7, 2012 at 3:10 PM, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> > wrote: > > > > From an idealistic point of view, it might be quite nice to have > several > > > live migrate mechanisms, so the user can choose whether they value > > minimum downtime, minimum network utilisation, or maximum safety. > > Agreed. IIRC, when post-copy was suggested for Xen years ago, > Ian Pratt was against it, though I don't recall why, so Michael > Hines work was never pursued (outside of academia). Probably > worth asking IanP before investing too much time into it. > > Was he against a hybrid approach, where you "push" things first, and then > "pull" things later? Or > just against a pure "pull" approach? I'm pretty sure a pure "pull" approach > would result in lower > performance during the migration. Sorry, I don't recall. > Just tossing another idea out there: What about throttling the VM if it's > dirtying too many pages? > You can use the "cap" feature of the credit1 scheduler to reduce the amount > of cpu time a given VM > gets, even if there is free cpu time available. You could play around with > doing N iterations, and > then cranking down the cap on each iteration after that; then the application > wouldn't have a several- > second pause, it would just be "running slowly" for some period of time. > > Overall doing a hybrid "send dirty pages for a while, then move and pull the > rest in" seems like the > best approach in the long-run, but it's fairly complicated. A throttling > approach is probably less > optimal but simpler to get working as a temporary measure. I agree there are lots of interesting hybrid possibilities worth exploring. There are side-effects to be considered though... for example, the current push approach is the only one that should be used when the goal of the migration is to evacuate a physical machine so that it can be powered off ASAP for maintenance or power management. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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