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    SubjectRe: [RFC] Unify KVM kernel-space and user-space code into a single project
    On 03/22/2010 02:17 AM, Ingo Molnar wrote:
    > * Anthony Liguori<> wrote:
    >> On 03/19/2010 03:53 AM, Ingo Molnar wrote:
    >>> * Avi Kivity<> wrote:
    >>>>> There were two negative reactions immediately, both showed a fundamental
    >>>>> server versus desktop bias:
    >>>>> - you did not accept that the most important usecase is when there is a
    >>>>> single guest running.
    >>>> Well, it isn't.
    >>> Erm, my usability points are _doubly_ true when there are multiple guests ...
    >>> The inconvenience of having to type:
    >>> perf kvm --host --guest --guestkallsyms=/home/ymzhang/guest/kallsyms \
    >>> --guestmodules=/home/ymzhang/guest/modules top
    >>> is very obvious even with a single guest. Now multiply that by more guests ...
    >> If you want to improve this, you need to do the following:
    >> 1) Add a userspace daemon that uses vmchannel that runs in the guest and can
    >> fetch kallsyms and arbitrary modules. If that daemon lives in
    >> tools/perf, that's fine.
    > Adding any new daemon to an existing guest is a deployment and usability
    > nightmare.
    Absolutely. In most cases it is not desirable, and you'll find that in a
    lot of cases it is not even possible - for non-technical reasons.
    One of the main benefits of virtualization is the ability to manage and
    see things from the outside.
    > The basic rule of good instrumentation is to be transparent. The moment we
    > have to modify the user-space of a guest just to monitor it, the purpose of
    > transparent instrumentation is defeated.
    Not to mention Heisenbugs and interference.


    > That was one of the fundamental usability mistakes of Oprofile.
    > There is no 'perf' daemon - all the perf functionality is _built in_, and for
    > very good reasons. It is one of the main reasons for perf's success as well.
    > Now Qemu is trying to repeat that stupid mistake ...
    > So please either suggest a different transparent solution that is technically
    > better than the one i suggested, or you should concede the point really.
    > Please try think with the heads of our users and developers and dont suggest
    > some weird ivory-tower design that is totally impractical ...
    > And no, you have to code none of this, we'll do all the coding. The only thing
    > we are asking is for you to not stand in the way of good usability ...
    > Thanks,
    > Ingo
    > --
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