linux-kernel - Re: [patch] measurements, numbers about CONFIG_OPTIMIZE

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Date:	Fri, 9 Jan 2009 09:11:47 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andi Kleen <andi@...stfloor.org>
cc:	Dirk Hohndel <hohndel@...radead.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	jim owens <jowens@...com>,
	Chris Mason <chris.mason@...cle.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	paulmck@...ux.vnet.ibm.com, Gregory Haskins <ghaskins@...ell.com>,
	Matthew Wilcox <matthew@....cx>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-btrfs <linux-btrfs@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nick Piggin <npiggin@...e.de>,
	Peter Morreale <pmorreale@...ell.com>,
	Sven Dietrich <SDietrich@...ell.com>, jh@...e.cz
Subject: Re: [patch] measurements, numbers about CONFIG_OPTIMIZE_INLINING=y
 impact



On Fri, 9 Jan 2009, Andi Kleen wrote:
> 
> There's also one alternative: gcc's inlining algorithms are extensibly
> tunable with --param. We might be able to find a set of numbers that
> make it roughly work like we want it by default.

We tried that.

IIRC, the numbers mean different things for different versions of gcc, and 
I think using the parameters was very strongly discouraged by gcc 
developers. IOW, they were meant for gcc developers internal tuning 
efforts, not really for external people. Which means that using them would 
put us _more_ at the mercy of random compiler versions rather than less.

			Linus
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