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

Ingo Molnar
2006-09-15T21:41:17Z

* 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