linux-kernel - Re: PS3: trouble with SPARSEMEM

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Date:	Mon, 10 Dec 2007 10:55:00 +0900
From:	Yasunori Goto <y-goto@...fujitsu.com>
To:	Geoff Levand <geoffrey.levand@...sony.com>
Cc:	Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>,
	Andrew Morton <akpm@...ux-foundation.org>, miltonm@....com,
	clameter@....com, apw@...dowen.org, linux-kernel@...r.kernel.org
Subject: Re: PS3: trouble with SPARSEMEM_VMEMMAP and kexec

> Yasunori Goto wrote:
> >> On Thu, 6 Dec 2007, Geert Uytterhoeven wrote:
> >> > On Thu, 6 Dec 2007, Yasunori Goto wrote:
> >> > > > I'll try Milton's suggestion to pre-allocate the memory early.  It seems
> >> > > > that should work as long as nothing else before the hot-plug mem is added
> >> > > > needs a large chunk.
> >> > > 
> >> > > Hello. Geoff-san. Sorry for late response.
> >> > > 
> >> > > Could you tell me the value of the following page_size calculation
> >> > > in vmemmap_populate()? I think this page_size may be too big value. 
> >> > > 
> >> > > ------
> >> > > int __meminit vmemmap_populate(struct page *start_page,
> >> > >                                        unsigned long nr_pages, int node)
> >> > >                            :
> >> > >                            :
> >> > >         unsigned long page_size = 1 << mmu_psize_defs[mmu_linear_psize].shift;
> >> > >                            :
> >> > > -------
> >> 
> >> 16 MiB of course.
> > 
> > 16 MiB is not page size. It is "section size". 
> > IIRC, powerpc's page size must be 4K (or 64K).
> > If page size is 4k, vmemmap_alloc_block will call the order 12 page.
> 
> 
> By default PS3 uses 4K virtual pages, and 16M linear pages.
> 
> 
> > Is it really correct value for vmemmap population?
> 
> 
> It seems vmemmap needs linear pages, so I think it is ok.

Oh, I see. Sorry for noise.

Bye.

-- 
Yasunori Goto 


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