Re: Tracing KVM with Systemtap

Stefan Hajnoczi
2010-09-21T13:33:54Z

On Tue, Sep 21, 2010 at 1:58 PM, Rayson Ho <rho@redhat.com> wrote:
> On Mon, 2010-09-20 at 14:36 +0100, Stefan Hajnoczi wrote:
>> Right now there are few pre-defined probes ("trace events" in QEMU
>> tracing speak).  As I develop I try to be mindful of new ones I create
>> and whether they would be generally useful.  I intend to contribute
>> more probes and hope others will too!
>
> I am still looking at/hacking the QEMU code. I have looked at the
> following places in the code that I think can be useful to have
> statistics gathered:
>
> net.c qemu_deliver_packet(), etc - network statistics

Yes.

> <CPU Arch>/op_helper.c global_cpu_lock(), tlb_fill() - lock & unlock,
> and TLB refill statistics

These are not relevant to KVM, they are only used when running with
KVM disabled (TCG mode).

> balloon.c, hw/virtio-balloon.c - ballooning information.

Prerna added a balloon event which is in qemu.git trace-events. Does
that one do what you need?

> I will see what other probes are useful for the end users. Also, are
> there developer documentations for KVM? (I googled but found a lot of
> presentations about KVM but not a lot of info about the internals.)

Not really. I suggest grabbing the source and following vl.c:main()
to the main KVM execution code.

Stefan