linux-kernel - Re: [patch 1/9] Guest page hinting: unused / free pages.

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Date:	Fri, 01 Sep 2006 17:43:40 +0200
From:	Martin Schwidefsky <schwidefsky@...ibm.com>
To:	Dave Hansen <haveblue@...ibm.com>
Cc:	linux-kernel@...r.kernel.org, virtualization@...ts.osdl.org,
	akpm@...l.org, nickpiggin@...oo.com.au, frankeh@...son.ibm.com,
	rhim@...gateh.edu
Subject: Re: [patch 1/9] Guest page hinting: unused / free pages.

On Fri, 2006-09-01 at 08:33 -0700, Dave Hansen wrote:
> > +++ linux-2.6-patched/mm/page_alloc.c   2006-09-01 12:49:35.000000000
> > +0200
> > @@ -515,6 +515,7 @@ static void __free_pages_ok(struct page 
> >                 reserved += free_pages_check(page + i);
> >         if (reserved)
> >                 return;
> > +       page_set_unused(page, order);
> >  
> >         kernel_map_pages(page, 1 << order, 0);
> >         local_irq_save(flags); 
> 
> Do these have anything in common with arch_free_page()?  I thought
> marking the pages as being "unused by the kernel" was the whole idea of
> having that hook.

This question did come up already. arch_free_page() is done before the
PageReserved() check so it isn't suitable for stable/unused state
transitions. You can argue that arch_free_page() should be moved but who
knows what the architecture defined function is supposed to do?
page_set_stable/page_set_unused on the other hand have a clearly defined
meaning.

-- 
blue skies,
  Martin.

Martin Schwidefsky
Linux for zSeries Development & Services
IBM Deutschland Entwicklung GmbH

"Reality continues to ruin my life." - Calvin.


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