linux-kernel - Re: RFC: How to handle function tracing, frame pointers and -mfentry?

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Message-ID: <4F9C1C31.7060507@zytor.com>
Date:	Sat, 28 Apr 2012 09:34:57 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-kbuild <linux-kbuild@...r.kernel.org>,
	Michal Marek <mmarek@...e.cz>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: RFC: How to handle function tracing, frame pointers and -mfentry?

On 04/28/2012 01:36 AM, Andi Kleen wrote:
> 
> Kconfig just needs to learn how to run the target compiler
> 
> I think that's the right direction. Right now our main
> Makefiles get polluted more and more with "test compiles", each
> of which makes a "null make" slower and slower. 
> 
> I just measured and a null compile (nothing changes) of a current
> tree calls "gcc" 141 times.
> 
> All this stuff should be cached in the Kconfig instead.
> 
> It may break some obscure setups (that can be probably fixed without
> too much effort), but the development turnaround improvement
> for everyone else would be worth it.
> 

I don't think it is a performance issue as much as a utility issue.
When Kconfig can't actually reflect what is built into the resulting
kernel, that is a problem.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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