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

Masami Hiramatsu
2010-03-16T23:02:28Z

oerg Roedel wrote:
> On Tue, Mar 16, 2010 at 12:25:00PM +0100, Ingo Molnar wrote:
>> Hm, that sounds rather messy if we want to use it to basically expose kernel
>> functionality in a guest/host unified way. Is the qemu process discoverable in
>> some secure way? Can we trust it? Is there some proper tooling available to do
>> it, or do we have to push it through 2-3 packages to get such a useful feature
>> done?
>
> Since we want to implement a pmu usable for the guest anyway why we
> don't just use a guests perf to get all information we want? If we get a
> pmu-nmi from the guest we just re-inject it to the guest and perf in the
> guest gives us all information we wand including kernel and userspace
> symbols, stack traces, and so on.

I guess this aims to get information from old environments running on
kvm for life extension :)

> In the previous thread we discussed about a direct trace channel between
> guest and host kernel (which can be used for ftrace events for example).
> This channel could be used to transport this information to the host
> kernel.

Interesting! I know the people who are trying to do that with systemtap.
See, http://vesper.sourceforge.net/

>
> The only additional feature needed is a way for the host to start a perf
> instance in the guest.

# ssh localguest perf record --host-chanel ... ? B-)

Thank you,

>
> Opinions?
>
>
> Joerg
>
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--
Masami Hiramatsu
e-mail: mhiramat@redhat.com