Peter Maydell writes: > On 27 July 2017 at 11:43, Daniel P. Berrange <berra...@redhat.com> wrote: >> Maybe I'm missing something, but aren't all these things >> already possible via either the statically defined tracepoints >> QEMU exposes, or by placing dynamic tracepoints on arbitrary >> code locations using dtrace/systemtap/lttng-ust.
> Last time I looked we didn't have tracepoints on most of > the events you'd be interested in. > That said, yes, I was going to ask if we could do this via > leveraging the tracepoint infrastructure and whatever scripting > facilities it provides. Are there any good worked examples of > this sort of thing? Can you do it as an ordinary non-root user? The hypertrace series I just sent contains an example that uses dtrace to trigger changes on the tracing state of events based on information from other events [1]. AFAIK it requires root privileges, and it's much less efficient than loading the instrumentation library proposed in this series (see that there's also an API to control event tracing). [1] https://lists.gnu.org/archive/html/qemu-devel/2017-07/msg08458.html Cheers, Lluis
