linux-kernel - Re: [bug] SLUB + mm/slab.c boot crash in -rc9

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Date:	Tue, 15 Apr 2008 14:43:12 -0700
From:	Mike Travis <travis@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Christoph Lameter <clameter@....com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org, Mel Gorman <mel@....ul.ie>,
	Nick Piggin <npiggin@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Yinghai.Lu@....com,
	apw@...dowen.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [bug] SLUB + mm/slab.c boot crash in -rc9

Ingo Molnar wrote:
> * Christoph Lameter <clameter@....com> wrote:
> 
>> On Tue, 15 Apr 2008, Ingo Molnar wrote:
>>
>>>> static DEFINE_PER_CPU(char, dummy)[10000];
>>> what's the guarantee that it's at the end of the section? I'd like 
>>> to pad the per cpu areas at their end. (doubling their size is a 
>>> good way to achieve that)
>> No guarantee. Its up to the linker. Sorry. We could add a new 
>> percpu.last section but that requires a number of changes to linking.
> 
> ah. Then the patch below should do the trick, right?
> 
> 	Ingo
> 
> ------------->
> Subject: larger: percpu
> From: Ingo Molnar <mingo@...e.hu>
> Date: Tue Apr 15 23:13:18 CEST 2008
> 
> Signed-off-by: Ingo Molnar <mingo@...e.hu>
> ---
>  arch/x86/kernel/vmlinux_32.lds.S |    1 +
>  1 file changed, 1 insertion(+)
> 
> Index: linux/arch/x86/kernel/vmlinux_32.lds.S
> ===================================================================
> --- linux.orig/arch/x86/kernel/vmlinux_32.lds.S
> +++ linux/arch/x86/kernel/vmlinux_32.lds.S
> @@ -186,6 +186,7 @@ SECTIONS
>  	__per_cpu_start = .;
>  	*(.data.percpu)
>  	*(.data.percpu.shared_aligned)
> +	. = . + 65536;
>  	__per_cpu_end = .;
>    }
>    . = ALIGN(PAGE_SIZE);

Or you could try this:

--- linux-2.6.x86.sched-last-0415.orig/include/linux/percpu.h
+++ linux-2.6.x86.sched-last-0415/include/linux/percpu.h
@@ -38,10 +38,7 @@

 /* Enough to cover all DEFINE_PER_CPUs in kernel, including modules. */
 #ifndef PERCPU_ENOUGH_ROOM
-#ifdef CONFIG_MODULES
-#define PERCPU_MODULE_RESERVE  8192
-#else
-#define PERCPU_MODULE_RESERVE  0
+#define PERCPU_MODULE_RESERVE  65536
 #endif

 #define PERCPU_ENOUGH_ROOM                                             \
--
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