Re: [PATCH] Enhance perf to collect KVM guest os statistics from host side

Avi Kivity
2010-03-16T13:37:21Z

On 03/16/2010 03:31 PM, Ingo Molnar wrote:
>
>> You can do that through libvirt, but that only works for guests started
>> through libvirt. libvirt provides command-line tools to list and manage
>> guests (for example autostarting them on startup), and tools built on top of
>> libvirt can manage guests graphically.
>>
>> Looks like we have a layer inversion here. Maybe we need a plugin system -
>> libvirt drops a .so into perf that teaches it how to list guests and get
>> their symbols.
>>
> Is libvirt used to start up all KVM guests? If not, if it's only used on some
> distros while other distros have other solutions then there's apparently no
> good way to get to such information, and the kernel bits of KVM do not provide
> it.
>

Developers tend to start qemu from the command line, but the majority of
users and all distros I know of use libvirt. Some users cobble up their
own scripts.

> To the user (and to me) this looks like a KVM bug / missing feature. (and the
> user doesnt care where the blame is) If that is true then apparently the
> current KVM design has no technically actionable solution for certain
> categories of features!
>

A plugin system allows anyone who is interested to provide the
information; they just need to write a plugin for their management tool.

Since we can't prevent people from writing management tools, I don't see
what else we can do.

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