Re: [patch for 2.6.26 0/7] Architecture Independent Markers

Ingo Molnar
2008-03-28T10:16:03Z

* KOSAKI Motohiro <m-kosaki@ceres.dti.ne.jp> wrote:

> > text data bss dec hex filename
> > 37642 7014 384 45040 aff0 sched.o.before
> > 37930 7134 384 45448 b188 sched.o.after
> >
> > 288 bytes for only 3 markers in the scheduler - that's 96 bytes added
> > per every marker (44 bytes of that in the fastpath).
> >
> > and the tracer codepath is now slower and more complex as well.
> >
> > A classic lose-lose situation, so let's apply this patch. Not!
> >
> > NACK-ed-by: Ingo Molnar <mingo@elte.hu>
>
> I wonder why nobody doesn't fix this serious problem until now. and I
> am interesting to what difference to ftrace and marker.

i warned and moaned about it ad nauseum.

furthermore, and because it's Friday again, let me remind folks that
SystemTap has an even more significant bloat problem: the fact that it
needs a huge download:

Installing:
kernel-debuginfo x86_64 2.6.25-0.163.rc7.git1.fc9
development-debuginfo 198 M
Installing for dependencies:
kernel-debuginfo-common x86_64 2.6.25-0.163.rc7.git1.fc9
development-debuginfo 30 M

Total download size: 229 M

for _every_ updated kernel. That 229 MB size reduces the user base of
SystemTap (which is otherwise a totally brilliant and cool tool) to 1%
of its potential userbase, to those truly desperate persons who really
_need_ to get their problem debugged somehow. But it's nowhere near
usable as an easy, ad-hoc kernel instrumentation tool, just due to the
sheer size it brings.

for heaven's sake, we can have 3 years of _full Linux kernel history_,
with all 87875 commits, with full changelog and dependencies and full
source code included, packed into a rather tight, 180 MB git repository
...

[ and then i havent even begun about the on-disk footprint of this
monstrum, after the packages have been installed: an additional 850 MB.
Puh-lease ... ]

there's a huge disconnect with reality here.

Ingo