From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <andi@firstfloor.org>
Subject: Re: [patch] measurements, numbers about CONFIG_OPTIMIZE_INLINING=y impact
Date: Fri, 9 Jan 2009 19:19:52 +0100
Message-ID: <20090109181952.GI26290@one.firstfloor.org>
References: <20090109130057.GA31845@elte.hu> <49675920.4050205@hp.com> <20090109153508.GA4671@elte.hu> <49677CB1.3030701@zytor.com> <20090109084620.3c711aad@infradead.org> <20090109172011.GD26290@one.firstfloor.org> <20090109172801.GC6936@parisc-linux.org> <20090109174719.GG26290@one.firstfloor.org> <20090109173914.GD6936@parisc-linux.org> <alpine.LFD.2.00.0901090947080.6528@localhost.localdomain>
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Cc: Matthew Wilcox <matthew@wil.cx>, Andi Kleen <andi@firstfloor.org>,
	Dirk Hohndel <hohndel@infradead.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@elte.hu>,
	jim owens <jowens@hp.com>,
	Chris Mason <chris.mason@oracle.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	paulmck@linux.vnet.ibm.com, Gregory Haskins <ghaskins@novell.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-btrfs <linux-btrfs@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Nick Piggin <npiggin@suse.de>,
	Peter Morreale <pmorreale@novell.com>,
	Sven Dietrich <SDietrich@novell.com>, jh@suse.cz,
	richard.guenther@gmail.com
To: Linus Torvalds <torvalds@linux-foundation.org>
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List-ID: <linux-btrfs.vger.kernel.org>

> So we do have special issues. And exactly _because_ we have special issues 
> we should also expect that some compiler defaults simply won't ever really 
> be appropriate for us.

I agree that the kernel needs quite different inlining heuristics
than let's say a template heavy C++ program. I guess that is 
also where our trouble comes from -- gcc is more tuned for the
later. Perhaps because the C++ programmers are better at working
with the gcc developers?

But it's also not inconceivable that gcc adds a -fkernel-inlining or
similar that changes the parameters if we ask nicely. I suppose
actually such a parameter would be useful for far more programs
than the kernel.

-Andi

-- 
ak@linux.intel.com