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    SubjectRE: [Qemu-devel] [RFC qemu 0/4] A PV solution for live migration optimization
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    > On Fri, Mar 04, 2016 at 06:51:21PM +0000, Dr. David Alan Gilbert wrote:
    > > * Paolo Bonzini (pbonzini@redhat.com) wrote:
    > > >
    > > >
    > > > On 04/03/2016 15:26, Li, Liang Z wrote:
    > > > >> >
    > > > >> > The memory usage will keep increasing due to ever growing
    > > > >> > caches, etc, so you'll be left with very little free memory fairly soon.
    > > > >> >
    > > > > I don't think so.
    > > > >
    > > >
    > > > Roman is right. For example, here I am looking at a 64 GB
    > > > (physical) machine which was booted about 30 minutes ago, and which
    > > > is running disk-heavy workloads (installing VMs).
    > > >
    > > > Since I have started writing this email (2 minutes?), the amount of
    > > > free memory has already gone down from 37 GB to 33 GB. I expect
    > > > that by the time I have finished running the workload, in two hours,
    > > > it will not have any free memory.
    > >
    > > But what about a VM sitting idle, or that just has more RAM assigned
    > > to it than is currently using.
    > > I've got a host here that's been up for 46 days and has been doing
    > > some heavy VM debugging a few days ago, but today:
    > >
    > > # free -m
    > > total used free shared buff/cache available
    > > Mem: 96536 1146 44834 184 50555 94735
    > >
    > > I very rarely use all it's RAM, so it's got a big chunk of free RAM,
    > > and yes it's got a big chunk of cache as well.
    >
    > One of the promises of virtualization is better resource utilization.
    > People tend to avoid purchasing VMs so much oversized that they never
    > touch a significant amount of their RAM. (Well, at least this is how things
    > stand in hosting market; I guess enterprize market is similar in this regard).
    >
    > That said, I'm not at all opposed to optimizing the migration of free memory;
    > what I'm trying to say is that creating brand new infrastructure specifically for
    > that case doesn't look justified when the existing one can cover it in addition
    > to much more common scenarios.
    >
    > Roman.

    Even the existing one can cover more common scenarios, but it has performance issue.
    that's why I create a new one.

    Liang

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