Re: [Qemu-devel] [PATCH v2 3/3] trace: instrument and trace tcg tb flush activity

[Paolo Bonzini]

Il 15/07/2014 22:29, Peter Maydell ha scritto:
> > >
> > > I think it's not a big deal if you always enable the counting, and perhaps
> > > show them in "info jit".
> We don't enable any other tracepoints by default; why would
> we want to enable just this one which is in a hot codepath??

I'm not referring to the tracepoint, only to trace_inc_counter instead 
of just "x++".  The overhead is probably not measurable. There are a few 
low-hanging fruit optimizations in cpu-exec.c that probably would give 
more measurable benefit, for example trying to replace cpu_loop_exit 
with a goto whenever possible.

Paolo