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    SubjectRe: [PATCH] Enhance perf to collect KVM guest os statistics from host side
    On 03/16/2010 08:08 AM, Ingo Molnar wrote:
    > * Avi Kivity<> wrote:
    >> On 03/16/2010 02:29 PM, Ingo Molnar wrote:
    >>> I mean, i can trust a kernel service and i can trust /proc/kallsyms.
    >>> Can perf trust a random process claiming to be Qemu? What's the trust
    >>> mechanism here?
    >> Obviously you can't trust anything you get from a guest, no matter how you
    >> get it.
    > I'm not talking about the symbol strings and addresses, and the object
    > contents for allocation (or debuginfo). I'm talking about the basic protocol
    > of establishing which guest is which.
    > I.e. we really want to be able users to:
    > 1) have it all working with a single guest, without having to specify 'which'
    > guest (qemu PID) to work with. That is the dominant usecase both for
    > developers and for a fair portion of testers.

    You're making too many assumptions.

    There is no list of guests anymore than there is a list of web browsers.

    You can have a multi-tenant scenario where you have distinct groups of
    virtual machines running as unprivileged users.

    > 2) Have some reasonable symbolic identification for guests. For example a
    > usable approach would be to have 'perf kvm list', which would list all
    > currently active guests:
    > $ perf kvm list
    > [1] Fedora
    > [2] OpenSuse
    > [3] Windows-XP
    > [4] Windows-7
    > And from that point on 'perf kvm -g OpenSuse record' would do the obvious
    > thing. Users will be able to just use the 'OpenSuse' symbolic name for
    > that guest, even if the guest got restarted and switched its main PID.

    Does "perf kvm list" always run as root? What if two unprivileged users
    both have a VM named "Fedora"?

    If we look at the use-case, it's going to be something like, a user is
    creating virtual machines and wants to get performance information about

    Having to run a separate tool like perf is not going to be what they
    would expect they had to do. Instead, they would either use their
    existing GUI tool (like virt-manager) or they would use their management
    interface (either QMP or libvirt).

    The complexity of interaction is due to the fact that perf shouldn't be
    a stand alone tool. It should be a library or something with a
    programmatic interface that another tool can make use of.


    Anthony Liguori

    > Is such a scheme possible/available? I suspect all the KVM configuration tools
    > (i havent used them in some time - gui and command-line tools alike) use
    > similar methods to ease guest management?
    > Ingo
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