Re: arch/x86/mm/ioremap unification grew by 10x
- From: "Huang, Ying" <ying.huang@xxxxxxxxx>
- Date: Mon, 18 Feb 2008 09:16:10 +0800
On Sun, 2008-02-17 at 19:09 +0000, Ian Campbell wrote:
On Fri, 2008-02-15 at 17:17 -0600, Matt Mackall wrote:
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.
551889a6e2a24a9c06fd453ea03b57b7746ffdc0 (the reason you CC'd me) only
changed this from unsigned long[1024] to pte_t[PAGE_SIZE/sizeof(pte_t)]
-static __initdata unsigned long bm_pte[1024]
+static __initdata pte_t bm_pte[PAGE_SIZE/sizeof(pte_t)]
__attribute__((aligned(PAGE_SIZE)));
I don't think that would have changed anything in this respect. It seems
to have been that way since 0947b2f31ca1ea1211d3cde2dbd8fcec579ef395
when it was added (Huang Ying CC'd).
Don't we have a special section for page-aligned crap so it doesn't
waste most of two pages?
We have .bss.page_aligned and it seems appropriate to use it.
But .bss.page_aligned is not an init section, this will waste some
memory after boot. Do you think that it is more appropriate to add
another section like .init.bss and .init.bss.page_aligned.
Best Regards,
Huang Ying
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