> Subject: Re: [RFC qemu 0/4] A PV solution for live migration optimization > > On (Thu) 03 Mar 2016 [18:44:24], Liang Li wrote: > > The current QEMU live migration implementation mark the all the > > guest's RAM pages as dirtied in the ram bulk stage, all these pages > > will be processed and that takes quit a lot of CPU cycles. > > > > From guest's point of view, it doesn't care about the content in free > > pages. We can make use of this fact and skip processing the free pages > > in the ram bulk stage, it can save a lot CPU cycles and reduce the > > network traffic significantly while speed up the live migration > > process obviously. > > > > This patch set is the QEMU side implementation. > > > > The virtio-balloon is extended so that QEMU can get the free pages > > information from the guest through virtio. > > > > After getting the free pages information (a bitmap), QEMU can use it > > to filter out the guest's free pages in the ram bulk stage. This make > > the live migration process much more efficient. > > > > This RFC version doesn't take the post-copy and RDMA into > > consideration, maybe both of them can benefit from this PV solution by > > with some extra modifications. > > I like the idea, just have to prove (review) and test it a lot to ensure we don't > end up skipping pages that matter. > > However, there are a couple of points: > > In my opinion, the information that's exchanged between the guest and the > host should be exchanged over a virtio-serial channel rather than virtio- > balloon. First, there's nothing related to the balloon here. > It just happens to be memory info. Second, I would never enable balloon in > a guest that I want to be performance-sensitive. So even if you add this as > part of balloon, you'll find no one is using this solution. > > Secondly, I suggest virtio-serial, because it's meant exactly to exchange free- > flowing information between a host and a guest, and you don't need to > extend any part of the protocol for it (hence no changes necessary to the > spec). You can see how spice, vnc, etc., use virtio-serial to exchange data. > > > Amit I don't like to use the virtio-balloon too, and it's confusing. It's grate if the virtio-serial can be used, I will take a look at it. Thanks for your suggestion! Liang -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
