linux-kernel - Re: [patch 10/10] Scheduler profiling

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Date:	Sat, 7 Jul 2007 04:25:26 +0200
From:	Adrian Bunk <bunk@...sta.de>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	Chuck Ebbert <cebbert@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	linux-kernel@...r.kernel.org, mbligh@...gle.com
Subject: Re: [patch 10/10] Scheduler profiling - Use immediate values

On Fri, Jul 06, 2007 at 07:43:15PM -0400, Mathieu Desnoyers wrote:
> * Adrian Bunk (bunk@...sta.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

-- 

       "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

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