[lttng-dev] Removing timing overhead with tracepoint() <-- query dropped by mailing list

[Mark E. Dawson, Jr.]

Ah, so there's more than just the one way I suggested in my original query. Perfect! Thanks, Mathieu!

      From: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
 To: "Mark E. Dawson, Jr." <medawsonjr at yahoo.com> 
Cc: lttng-dev <lttng-dev at lists.lttng.org>; Michael Jeanson <mjeanson at efficios.com>
 Sent: Thursday, November 17, 2016 2:47 PM
 Subject: Re: Removing timing overhead with tracepoint() <-- query dropped by mailing list
   
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----- On Nov 17, 2016, at 12:21 PM, Mark E. Dawson, Jr. <medawsonjr at yahoo.com> wrote:

Mathieu,
My query appears to be getting dropped by the mailing list, forcing me to ask you directly which I understand is both inefficient and a nuisance. We met when I spoke (along with Christoph Lameter) at the Tracing Summit a couple years back.

Hi Mark,

Not sure why the mailing list would have dropped your email. Everything looks fine in theadmin interface. Adding it in CC. (Michael, can you check if lttng-dev has issues with emailsfrom yahoo domains ?)
Anyway, my question is as follows:
If I want to remove a ton of compiled-in calls to an "rdtsc-based" C timing function and make them all conditionally-enabled based on whether or not I enable a tracing session, I can do so by adding the aforementioned "rdtsc" call as one of the arguments to tracepoint() along with our defined provider and event name, correct?

You can take a few approaches there:

1) Use if (tracepoint_enabled()) { ..read tsc... do_tracepoint(...); }

2) do this function call or static inline invocation as an argument of tracepoint().

3) do the function call/static inline invocation within the tracepoint probe provider
     (TRACEPOINT_EVENT() code).

Let me know if I somehow misunderstood the intent of your question.

Thanks,

Mathieu
-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com

   
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