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

From: Avi Kivity
Date: Tue Mar 16 2010 - 09:37:56 EST


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.

--
error compiling committee.c: too many arguments to function

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