Re: Tracing KVM with Systemtap

[Rayson Ho <rho@redhat.com>]

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

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

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

Besides the ballooning part, which I know what it is but don't fully
understand how it works, the other parts can be implemented as Systemtap
tapsets (~ "DTrace scripts") in the initial stage.

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.)

Rayson



> 
> Prerna is also looking at adding useful probes.
> 
> Stefan