Messages in this thread | | | Date | Thu, 3 Jan 2008 12:42:17 -0500 (EST) | From | Steven Rostedt <> | Subject | Re: [RFC PATCH 00/11] mcount tracing utility |
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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
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