[lttng-dev] [Qemu-devel] [PATCH 0/6] hypertrace: Lightweight guest-to-QEMU trace channel

Stefan Hajnoczi stefanha at redhat.com
Thu Aug 18 13:53:27 UTC 2016

On Thu, Aug 18, 2016 at 12:22:18PM +0200, Lluís Vilanova wrote:
> Stefan Hajnoczi writes:
> > On Fri, Aug 05, 2016 at 06:59:23PM +0200, Lluís Vilanova wrote:
> >> The hypertrace channel allows guest code to emit events in QEMU (the host) using
> >> its tracing infrastructure (see "docs/trace.txt"). This works in both 'system'
> >> and 'user' modes. That is, hypertrace is to tracing, what hypercalls are to
> >> system calls.
> >> 
> >> You can use this to emit an event on both guest and QEMU (host) traces to easily
> >> synchronize or correlate them. You could also modify you guest's tracing system
> >> to emit all events through the hypertrace channel, providing a unified and fully
> >> synchronized trace log. Another use case is timing the performance of guest code
> >> when optimizing TCG (QEMU traces have a timestamp).
> >> 
> >> See first commit for a full description.
> >> 
> >> Signed-off-by: Lluís Vilanova <vilanova at ac.upc.edu>
> >> ---
> > CCing Steven Rostedt, Masami Hiramatsu, Luiz Capitulino, and LTTng folks
> > who have all looked into host/guest tracing solutions.
> [...]
> Oh, I wasn't aware of that. I'm certainly interested in collaborating.

They are working on or have worked on different approaches to host/guest
tracing.  Unfortunately there isn't an out-of-the-box solution as far as
I know.

It would be nice if there was a documented host/guest tracing approach
that didn't involve much manual setup and handled most use cases.

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