Re: [Qemu-devel] memory trace with qemu

[Stefan Hajnoczi]

On Fri, Jul 23, 2010 at 8:25 AM, Mulyadi Santosa
<address@hidden> wrote:
> On Fri, Jul 23, 2010 at 13:15, Stefan Hajnoczi <address@hidden> wrote:
>> Thanks Mulyadi, I think you are referring to the tracing work that
>> Prerna Saxena and I are doing.  Here is the documentation:
>>
>> http://repo.or.cz/w/qemu/stefanha.git/blob/tracing:/docs/tracing.txt
>
> You're welcome Stefan :) I just hate to see people reinvent the wheel,
> even for "holy and sacred" purpose :)
>
> This makes me believe that Qemu is indeed an (almost) ideal platform
> to do system tracing, given that it is open source and support many
> many cpu architecture. Possibly in the future (or now?), it would be a
> standard for binary analysis platform.
>
> my own question: any benchmark to show us the overhead of each of
> these tracing frameworks/patches?

It depends on the trace backend you choose.  Currently there is the
"simple" backend, which is portable and built into the source tree to
offer core functionality, and the "ust" backend, which uses the LTTng
Userspace Tracer for fancier but fussier tracing on Linux.

The performance of these backends is different.  If performance is a
top concern, then the "ust" backend is probably the way to go.  See
http://lttng.org/ust for more info.

However, I have successfully used the simple backend for block layer
latency tracing: http://www.linux-kvm.org/page/Virtio/Block/Latency.

Stefan

> --
> regards,
>
> Mulyadi Santosa
> Freelance Linux trainer and consultant
>
> blog: the-hydra.blogspot.com
> training: mulyaditraining.blogspot.com
>