linux-kernel - Re: [RFC] Tight check of pfn

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Message-Id: <20100713170222.9369e649.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 13 Jul 2010 17:02:22 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Minchan Kim <minchan.kim@...il.com>,
	Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Shaohua Li <shaohua.li@...el.com>,
	Yakui Zhao <yakui.zhao@...el.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	arm-kernel@...ts.infradead.org, kgene.kim@...sung.com,
	Mel Gorman <mel@....ul.ie>
Subject: Re: [RFC] Tight check of pfn_valid on sparsemem

On Tue, 13 Jul 2010 16:58:08 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:

> On Tue, 13 Jul 2010 16:34:17 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> 
> > Anyway, sparsemem is designed to be aligned to SECTION_SIZE of memmap.
> > Please avoid adding new Spaghetti code without proper configs.
> > Thanks,
> 
> Ok, I realized I misunderstand all. Arm doesn't unmap memmap but reuse the page
> for memmap without modifing ptes. My routine only works when ARM uses sparsemem_vmemmap.
> But yes, it isn't.
> 
> Hmm...How about using pfn_valid() for FLATMEM or avoid using SPARSEMEM ?
> If you want conrols lower than SPARSEMEM, FLATMEM works better because ARM unmaps memmap.
                      allocation of memmap in lower granule than SPARSEMEM.


How about stop using SPARSEMEM ? What's the benefit ? It just eats up memory for
mem_section[].

Sorry,
-Kame

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