Re: [patch 10/10] Scheduler profiling - Use immediate values

Adrian Bunk
2007-07-07T02:25:24Z

On Fri, Jul 06, 2007 at 07:43:15PM -0400, Mathieu Desnoyers wrote:
> * Adrian Bunk (bunk@stusta.de) wrote:
> > On Fri, Jul 06, 2007 at 06:14:10PM -0400, Chuck Ebbert wrote:
> > > On 07/06/2007 07:44 AM, Andi Kleen wrote:
> > > > I think the optimization is a good idea, although i dislike it
> > > > that it is complicated for the dynamic markers. If it was just
> > > > static it would be much simpler.
> > >
> > > Another thing to consider is that there might be hundreds of these
> > > probes/tracepoints active in an instrumented kernel. The overhead
> > > adds up fast, so the gain may be worth all the pain.
> >
> > Only if you want to squeeze the last bit of performance out of
> > _debugging_ functionality.
> >
> > You avoid all the pain if you simply don't use debugging functionality
> > on production systems.
> >
>
> Adrian,
>
> Please have a look at my markers posts, especially:
>
> http://www.ussg.iu.edu/hypermail/linux/kernel/0707.0/0669.html
>
> And also look into OLS 2007 proceedings for Martin Bligh's paper on
> Debugging Google sized clusters. It basically makes the case for adding
> functionnality to debug _user space_ problems on production systems that
> can be turned on dynamically.

Using a different kernel for tracing still fulfills all the requirements
listed in section 5 of your paper...

> Mathieu

cu
Adrian

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