linux-kernel - Re: PS3: trouble with SPARSEMEM

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Message-Id: <20071206191717.6955.Y-GOTO@jp.fujitsu.com>
Date:	Thu, 06 Dec 2007 19:48:11 +0900
From:	Yasunori Goto <y-goto@...fujitsu.com>
To:	Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>
Cc:	Geoff Levand <geoffrey.levand@...sony.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

> 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;
> > >                            :
> > > -------
> > 
> > 24 MiB
> 
> Bummer, messing up bits and MiB.
> 
> 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.

Is it really correct value for vmemmap population?

> PS3 initially starts with 128 MiB.
> Later hotplug is used to add the remaining memory (96 or 112 MIB, IIRC).

Ok.
Then, add_memory() must be called 6 or 7 times for each sections.

Thanks.


-- 
Yasunori Goto 


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