linux-kernel - Re: [PATCH repost] mm,x86: remove debug_pagealloc

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Date:	Tue, 6 Dec 2011 08:55:31 +0100
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-mm@...ck.org, x86@...nel.org, linux-kernel@...r.kernel.org,
	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH repost] mm,x86: remove debug_pagealloc_enabled

On Mon, Dec 05, 2011 at 04:54:34PM +0100, Ingo Molnar wrote:
> 
> * Stanislaw Gruszka <sgruszka@...hat.com> wrote:
> 
> > On Mon, Dec 05, 2011 at 12:06:56PM +0100, Ingo Molnar wrote:
> > > 
> > > * Stanislaw Gruszka <sgruszka@...hat.com> wrote:
> > > 
> > > > When (no)bootmem finish operation, it pass pages to buddy allocator.
> > > > Since debug_pagealloc_enabled is not set, we will do not protect pages,
> > > > what is not what we want with CONFIG_DEBUG_PAGEALLOC=y.
> > > > 
> > > > To fix remove debug_pagealloc_enabled. That variable was introduced by
> > > > commit 12d6f21e "x86: do not PSE on CONFIG_DEBUG_PAGEALLOC=y" to get
> > > > more CPA (change page attribude) code testing. But currently we have
> > > > CONFIG_CPA_DEBUG, which test CPA.
> > > > 
> > > > Signed-off-by: Stanislaw Gruszka <sgruszka@...hat.com>
> > > > Acked-by: Mel Gorman <mgorman@...e.de>
> > > > ---
> > > >  arch/x86/mm/pageattr.c |    6 ------
> > > >  include/linux/mm.h     |   10 ----------
> > > >  init/main.c            |    5 -----
> > > >  mm/debug-pagealloc.c   |    3 ---
> > > >  4 files changed, 0 insertions(+), 24 deletions(-)
> > > 
> > > I'm getting this boot crash with the patch applied:
> > 
> > I'm sorry for breaking the boot. I tried to reproduce problem 
> > on my laptop, but failed. I plan to test patch with your 
> > config on some other machines.
> > 
> > On the meantime can you test attached incremental patch and 
> > see if it workaround the crash? I suspect memblock reuse pages 
> > that it passed already to buddy allocator.
> 
> That will take some time - so if you could try my config on 
> another box that would be great. There isnt anything special 
> about that box.

I reproduced with limiting memory via mem=1G and increase
find_range_array count argument, what caused "struct range"
array was bigger and needed more memory. With that I can
confirm that previous patch fixes the problem. I think
it's the simplest possible fix, I'll post patch with 
changelog and comment in the next email.

Stanislaw 
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