On 12/30/2011 12:39 AM, Anthony Liguori wrote: > On 12/28/2011 07:25 PM, Isaku Yamahata wrote: >> Intro >> ===== >> This patch series implements postcopy live migration.[1] >> As discussed at KVM forum 2011, dedicated character device is used for >> distributed shared memory between migration source and destination. >> Now we can discuss/benchmark/compare with precopy. I believe there are >> much rooms for improvement. >> >> [1] http://wiki.qemu.org/Features/PostCopyLiveMigration >> >> >> Usage >> ===== >> You need load umem character device on the host before starting migration. >> Postcopy can be used for tcg and kvm accelarator. The implementation depend >> on only linux umem character device. But the driver dependent code is split >> into a file. >> I tested only host page size == guest page size case, but the implementation >> allows host page size != guest page size case. >> >> The following options are added with this patch series. >> - incoming part >> command line options >> -postcopy [-postcopy-flags<flags>] >> where flags is for changing behavior for benchmark/debugging >> Currently the following flags are available >> 0: default >> 1: enable touching page request >> >> example: >> qemu -postcopy -incoming tcp:0:4444 -monitor stdio -machine accel=kvm >> >> - outging part >> options for migrate command >> migrate [-p [-n]] URI >> -p: indicate postcopy migration >> -n: disable background transferring pages: This is for benchmark/debugging >> >> example: >> migrate -p -n tcp:<dest ip address>:4444 >> >> >> TODO >> ==== >> - benchmark/evaluation. Especially how async page fault affects the result. > > I'll review this series next week (Mike/Juan, please also review when you > can). > > But we really need to think hard about whether this is the right thing to > take into the tree. I worry a lot about the fact that we don't test pre-copy > migration nearly enough and adding a second form just introduces more things > to test. > > It's also not clear to me why post-copy is better. If you were going to sit > down and explain to someone building a management tool when they should use > pre-copy and when they should use post-copy, what would you tell them?
Start with pre-copy , if it doesn't converge switch to post-copy Orit > > Regards, > > Anthony Liguori >
