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

[Mathieu Desnoyers]

* Adrian Bunk (bunk@xxxxxxxxx) 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.

Mathieu

> cu
> Adrian
> 
> -- 
> 
>        "Is there not promise of rain?" Ling Tan asked suddenly out
>         of the darkness. There had been need of rain for many days.
>        "Only a promise," Lao Er said.
>                                        Pearl S. Buck - Dragon Seed
> 

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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