linux-kernel - Re: [patch 1/9] Conditional Calls

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Message-ID: <20070620215927.GA25495@Krystal>
Date:	Wed, 20 Jun 2007 17:59:27 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Adrian Bunk <bunk@...sta.de>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 1/9] Conditional Calls - Architecture Independent Code

* Adrian Bunk (bunk@...sta.de) wrote:
> On Thu, Jun 14, 2007 at 12:02:42PM -0400, Mathieu Desnoyers wrote:
> >...
> > Well, we must take into account where these markers are added and how
> > often the marked code is run. Since I mark very highly used code paths
> > (interrupt handlers, page faults, lockdep code) and also plan to mark
> > other code paths like the VM subsystem, adding cycles to these code
> > paths seems like a no-go solution for standard distribution kernels.
> >...
> > People can get really picky when they have to decide wether or not they
> > compile-in a profiling or tracing infrastructure in a distribution
> > kernel.  If the impact is detectable when they are not doing any tracing
> > nor profiling, their reflex will be to compile it out so they can have
> > the "maximum performance". This is why I am going through the trouble of
> > making the markers impact as small as possible.
> 
> Now that we finally hear what this code is required for, can we discuss 
> on this basis whether this is wanted and required?
> 
> Including the question which abuse possibilities such an infrastructure 
> offers, and whether this is wanted in distribution kernels.
> 

Hi Adrian,

The purpose of this infrastructure has never been a secret; it is a
piece taken from the Linux Kernel Markers. I proposed the first
implementation of markers in December 2006.

Please use the following link as a starting point to the thorough
discussion that has already been held on this matter.

First, a huge discussion thread back in November 2006, where the need
for a marker infrastructure has been recognized:
http://lwn.net/Articles/200059/

A good summary of my recent previous post on kerneltrap:
http://kerneltrap.org/node/8186

If you have new specific concerns to bring forward, I will be glad to
discuss them with you.

Regards,

Mathieu

-- 
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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