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

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Date:	Thu, 7 Aug 2008 21:21:18 -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, Roland McGrath wrote:

> > This doesn't seem any less complex than what I did. With this, I would 
> > have to come up with another way to handle modules. This will make
> > things a lot more complex.
> 
> 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.

-- Steve

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