[Qemu-devel] Reg. trace infrastructure

[Sripathi Kodi]

Hi Stefan, Prerna,

I pulled down QEMU tracing code from git://repo.or.cz/qemu/stefanha.git
and tried to use it to trace something in virtio-9p code. I don't have
any knowledge of how traces are implemented and I just went with the
documentation. With help from Prerna, I was able to insert a trace
point and observe it getting hit from the QEMU monitor. However, I have
a few questions about this. Could you please help me out?

*) My understanding is the traces are dumped to a file only when the
trace buffer gets filled. Is there a way to: 
  a) Forcibly dump the contents of the buffer when needed.
  b) When QEMU exits it should dump the buffer. Doesn't seem to be
  doing this now.
  c) A way to specify the file into which it writes the traces.

*) Is QEMU monitor the only way to enable/disable trace points? Is it
possible to programmatically enable/disable trace points from within
QEMU code? If that is not possible, is it possible to specify all trace
points to be enabled in a text file and ask QEMU to read the file when
it starts up?

*) Is it possible to enable/disable a bunch of trace points at one
shot? Can trace points be grouped in some way? Can I say "enable all
trace points in a particular .c file" or "enable all trace points in
these 2 functions"?

Thanks a lot for your help.

-Sripathi.