Re: [PATCH 0/11] LTTng-core (basic tracing infrastructure) 0.5.108

Tim Bird
2006-09-15T16:59:19Z

Alan Cox wrote:
> Ar Gwe, 2006-09-15 am 10:35 -0400, ysgrifennodd Karim Yaghmour:
>> @@ -1709,6 +1712,7 @@ switch_tasks:
>> ++*switch_count;
>>
>> prepare_arch_switch(rq, next);
>> + TRACE_SCHEDCHANGE(prev, next);
>> prev = context_switch(rq, prev, next);
>> barrier();
>
> All we appear to lack is systemtap ability to parse debug data so it can
> be told "trace on line 9 of sched.c and record rq and next"

If the latter is a suggestion for how an out-of-tree rule for a
tracepoint definition should look, it's a terrible one.
Alan's example is much more fragile, from a maintenance perspective,
than Karim's. Plus, it's much more difficult to implement, whether
you plan to inject no-ops at compile time, just record locations and
stack offsets, or actually place some tracing code (heaven forbid)
that the compiler could optimize for that context.

I still think that this is off-topic for the patch posted. I think we
should debate the implementation of tracepoints/markers when someone posts a
patch for some. I think it's rather scurrilous to complain about
code NOT submitted. Ingo has even mis-characterized the not-submitted
instrumentation patch, by saying it has 350 tracepoints when it has no
such thing. I counted 58 for one architecture (with only 8 being
arch-specific).
-- Tim

=============================
Tim Bird
Architecture Group Chair, CE Linux Forum
Senior Staff Engineer, Sony Electronics
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