linux-kernel - Re: [PATCH 0/5] ftrace: to kill a daemon

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Date:	Thu, 7 Aug 2008 21:24:10 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Roland McGrath <roland@...hat.com>
cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	Ulrich Drepper <drepper@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Gregory Haskins <ghaskins@...ell.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>,
	Clark Williams <williams@...hat.com>,
	Sam Ravnborg <sam@...nborg.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH 0/5] ftrace: to kill a daemon


On Thu, 7 Aug 2008, Steven Rostedt wrote:
> On Thu, 7 Aug 2008, Roland McGrath wrote:
> > 
> > The scheme you've implemented can apply fine to a .ko file after it's made.
> > They are just .o's really.  It is presumably faster to do one step per
> > final .ko rather than many tiny ones (per source file).  
> > 
> > That might be a benefit to doing it all at the end for vmlinux too.  I
> > think the best way would be to have a vmlinux.o that we actually use in the
> > link, rather than just analyzing and discarding.  Then you can just do your
> > existing hack on vmlinux.o before it's linked into vmlinux.
> 
> OK, I am playing with this. And you are right, it does work with vmlinux.o 
> file.  It adds almost another minute to the build anytime something is 
> changed. Where the per-object way may take longer doing a full build, but 
> does not add that extra minute ever build.
> 
> Which would people prefer?  I little longer full build and do the 
> modification on every object, or have a shorter full build, but every 
> build will take that extra minute to do?
> 
> Note, if you have DYNMAIC_FTRACE disabled, this is a nop, and will _not_ 
> affect you.

Another advantage of doing it at the end on the vmlinux.o, is that you do 
not need to recompile the entire kernel when you change the config option. 
But you do need to recompile all modules.

-- Steve

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