On Thu, 3 Jan 2008, Mathieu Desnoyers wrote: > Hi Steven, > > Great work! Thanks! > > (added Tim Bird, author of KFT/KFI to the CC list) I'm currently investigating using -finstrument-functions instead of -pg, but if the overhead is too much, I may try to incorporate both. > > One interesting aspect of LTTng is that is would be very lightweight. > You seem to use interrupt disabling with your simple tracer and do a > _lot_ of cacheline bouncing (trace_idx[NR_CPUS] is a very good exemple). Please note that this tracer is more of a "simple example". There's lots of improvements that can be made. It was meant more of to show what mcount can bring than to push the tracer itself. I want to stress that the tracer in this patch set is a *much* simplified version of the latency_tracer in the RT patch. I want to start out simple, complexity can come later ;-) > > LTTng would write the information to a per-cpu memory buffer in binary > format. I see that it would be especially useful in flight recorder > mode, where we overwrite the buffers without writing them to disk : when > a problematic condition is reached, (a kernel oops would be a good one), > then we just stop tracing and dump the last buffers to disk. In this > case, we would have the last function calls that led to an OOPS. This sounds great. My hope is that we can get the mcount (or cyg_profile) functionality in the kernel that many different users can deploy. -- Steve - To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
