linux-kernel - Re: arch/x86/mm/ioremap unification grew by 10x

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Message-Id: <1203117425.12383.238.camel@cinder.waste.org>
Date:	Fri, 15 Feb 2008 17:17:05 -0600
From:	Matt Mackall <mpm@...enic.com>
To:	Sam Ravnborg <sam@...nborg.org>
Cc:	Linux Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Ian Campbell <ijc@...lion.org.uk>
Subject: Re: arch/x86/mm/ioremap unification grew by 10x


On Fri, 2008-02-15 at 15:21 -0600, Matt Mackall wrote:
> On Fri, 2008-02-15 at 21:32 +0100, Sam Ravnborg wrote:
> > On Fri, Feb 15, 2008 at 02:25:54PM -0600, Matt Mackall wrote:
> > > In 2.6.24 defconfig, my build stats show ioremap_32.o was 1.8k. In
> > > 2.6.25-rc1, the unified ioremap.o is 20.8k.
> > 
> > Just an observation - 17 commits touches said file after
> > the unification (at least in latest -linus).
> 
> Correction: those numbers should be halved. So we're going from .9k to
> 10.4k.

And here's most of the cause:

000002b8 00000124 T early_ioremap
00001000 00001000 t bm_pte
00002000 00000004 T early_ioremap_debug

static __initdata pte_t bm_pte[PAGE_SIZE/sizeof(pte_t)]
				__attribute__((aligned(PAGE_SIZE)));

Double ouch. First, this isn't in BSS. Second, even though it's
initdata, the alignment slop won't get recovered.

Don't we have a special section for page-aligned crap so it doesn't
waste most of two pages?

-- 
Mathematics is the supreme nostalgia of our time.

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