RE: [Qemu-devel] [PATCH kernel v5 0/5] Extend virtio-balloon for fast (de)inflating & fast live migration
From: Li, Liang Z
Date: Thu Dec 15 2016 - 19:49:29 EST
> Subject: Re: [Qemu-devel] [PATCH kernel v5 0/5] Extend virtio-balloon for
> fast (de)inflating & fast live migration
> On 12/14/2016 12:59 AM, Li, Liang Z wrote:
> >> Subject: Re: [Qemu-devel] [PATCH kernel v5 0/5] Extend virtio-balloon
> >> for fast (de)inflating & fast live migration
> >> On 12/08/2016 08:45 PM, Li, Liang Z wrote:
> >>> What's the conclusion of your discussion? It seems you want some
> >>> statistic before deciding whether to ripping the bitmap from the
> >>> ABI, am I right?
> >> I think Andrea and David feel pretty strongly that we should remove
> >> the bitmap, unless we have some data to support keeping it. I don't
> >> feel as strongly about it, but I think their critique of it is pretty
> >> valid. I think the consensus is that the bitmap needs to go.
> >> The only real question IMNHO is whether we should do a power-of-2 or
> >> a length. But, if we have 12 bits, then the argument for doing
> >> length is pretty strong. We don't need anywhere near 12 bits if doing
> > Just found the MAX_ORDER should be limited to 12 if use length instead
> > of order, If the MAX_ORDER is configured to a value bigger than 12, it
> > will make things more complex to handle this case.
> > If use order, we need to break a large memory range whose length is
> > not the power of 2 into several small ranges, it also make the code complex.
> I can't imagine it makes the code that much more complex. It adds a for loop.
Yes, just a little. :)
> > It seems we leave too many bit for the pfn, and the bits leave for
> > length is not enough, How about keep 45 bits for the pfn and 19 bits
> > for length, 45 bits for pfn can cover 57 bits physical address, that should be
> enough in the near feature.
> > What's your opinion?
> I still think 'order' makes a lot of sense. But, as you say, 57 bits is enough for
> x86 for a while. Other architectures.... who knows?