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

[Ingo Molnar <mingo@elte.hu>]

* Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:

> * Ingo Molnar (mingo@elte.hu) wrote:
> > sorry, but i disagree. There _is_ a solution that is superior in every 
> > aspect: kprobes + SystemTap. (or any other equivalent dynamic tracer)
> > 
> 
> I am sorry to have to repeat myself, but this is not true for heavy 
> loads.

djprobes?

> > > At this point you've been rather uncompromising [...]
> > 
> > yes, i'm rather uncompromising when i sense attempts to push inferior 
> > concepts into the core kernel _when_ a better concept exists here and 
> > today. Especially if the concept being pushed adds more than 350 
> > tracepoints that expose something to user-space that amounts to a 
> > complex external API, which tracepoints we have little chance of ever 
> > getting rid of under a static tracing concept.
> > 
> From an earlier email from Tim bird :
> 
> "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)."

i missed that (way too many mails in this thread).

Here is how i counted them:

 $ grep "\<trace_.*(" * | wc -l
 359

some of those are not true tracepoints, but there's at least this many 
of them:

 $ grep "\<trace_.*(" *instrumentation* | wc -l
 235

so the real number is somewhere between.

 patch-2.6.17-lttng-0.5.108-instrumentation-arm.diff
 patch-2.6.17-lttng-0.5.108-instrumentation.diff
 patch-2.6.17-lttng-0.5.108-instrumentation-i386.diff
 patch-2.6.17-lttng-0.5.108-instrumentation-mips.diff
 patch-2.6.17-lttng-0.5.108-instrumentation-powerpc.diff
 patch-2.6.17-lttng-0.5.108-instrumentation-ppc.diff
 patch-2.6.17-lttng-0.5.108-instrumentation-s390.diff
 patch-2.6.17-lttng-0.5.108-instrumentation-sh.diff
 patch-2.6.17-lttng-0.5.108-instrumentation-x86_64.diff

when judging kernel maintainance overhead, the sum of all patches 
matters. And i considered all the other patches too (the ones that add 
actual tracepoints) that will come after the currently offered ones, not 
just the ones you submitted to lkml.

	Ingo