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Message-ID: <alpine.DEB.1.10.0901091631500.17378@gandalf.stny.rr.com>
Date: Fri, 9 Jan 2009 16:33:04 -0500 (EST)
From: Steven Rostedt <rostedt@...dmis.org>
To: Theodore Tso <tytso@....edu>
cc: Richard Guenther <richard.guenther@...il.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Matthew Wilcox <matthew@....cx>,
Andi Kleen <andi@...stfloor.org>,
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>,
paulmck@...ux.vnet.ibm.com, Gregory Haskins <ghaskins@...ell.com>,
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, Theodore Tso wrote:
> I'm beginning to think that for the kernel, we should just simply
> remove CONFIG_OPTIMIZE_INLINING (so that inline means
> "always_inline"), and -fno-inline-functions
> -fno-inline-functions-called-one (so that gcc never inlines functions
> behind our back) --- and then we create tools that count how many times functions get used, and how big functions are, so that we can flag if some
> function really should be marked inline when it isn't or vice versa.
>
> But given that this is a very hard thing for an automated program
> todo, let's write some tools so we can easily put a human in the loop,
> who can add or remove inline keywords where it makes sense, and let's
> give up on gcc being able to "guess" correctly.
>
> For some things, like register allocation, I can accept that the
> compiler will usually get these things right. But whether or not to
> inline a function seems to be one of those things that humans (perhaps
> with some tools assist) can still do a better job than compilers.
Adding a function histogram in ftrace should be trivial. I can write one
up if you want. It will only count the functions not inlined.
-- Steve
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