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Date: Tue, 15 Apr 2008 12:39:26 -0700 (PDT)
From: Christoph Lameter <clameter@sgi.com>
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To: Ingo Molnar <mingo@elte.hu>
cc: Linus Torvalds <torvalds@linux-foundation.org>,
       Pekka Enberg <penberg@cs.helsinki.fi>, linux-kernel@vger.kernel.org,
       Mel Gorman <mel@csn.ul.ie>, Nick Piggin <npiggin@suse.de>,
       Andrew Morton <akpm@linux-foundation.org>,
       "Rafael J. Wysocki" <rjw@sisk.pl>, Yinghai.Lu@sun.com
Subject: Re: [bug] SLUB + mm/slab.c boot crash in -rc9
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On Tue, 15 Apr 2008, Linus Torvalds wrote:

> On Tue, 15 Apr 2008, Ingo Molnar wrote:
> > 
> > btw., now with a second full day spent on this regression, i have 
> > figured out a workaround the hard way: increasing SECTION_SIZE_BITS in 
> > include/asm-x86/sparsemem.h from 26 to 27 makes it go away.
> 
> Interesting.

Hmmmm. SECTION_SIZE_BITS == 26 means SECTIONS_SHIFT == 6. 
Increasing SECTION_SIZE_BITS to 27 reduces SECTION_SHIFT to 5. Thereby 
the number of sparsemem sections (NR_MEM_SECTIONS) is reduced to half (64 
to 32).