From: Hugh Dickins <hugh.dickins@tiscali.co.uk>
To: Nitin Gupta <ngupta@vflare.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-mm-cc@laptop.org
Subject: Re: [PATCH 1/4] compcache: xvmalloc memory allocator
Date: Mon, 24 Aug 2009 21:39:02 +0100 (BST) [thread overview]
Message-ID: <Pine.LNX.4.64.0908242132320.8144@sister.anvils> (raw)
In-Reply-To: <4A92EBB4.1070101@vflare.org>
On Tue, 25 Aug 2009, Nitin Gupta wrote:
> On 08/24/2009 11:03 PM, Pekka Enberg wrote:
> >
> > What's the purpose of passing PFNs around? There's quite a lot of PFN
> > to struct page conversion going on because of it. Wouldn't it make
> > more sense to return (and pass) a pointer to struct page instead?
>
> PFNs are 32-bit on all archs
Are you sure? If it happens to be so for all machines built today,
I think it can easily change tomorrow. We consistently use unsigned long
for pfn (there, now I've said that, I bet you'll find somewhere we don't!)
x86_64 says MAX_PHYSMEM_BITS 46 and ia64 says MAX_PHYSMEM_BITS 50 and
mm/sparse.c says
unsigned long max_sparsemem_pfn = 1UL << (MAX_PHYSMEM_BITS-PAGE_SHIFT);
Hugh
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next prev parent reply other threads:[~2009-08-25 22:04 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-08-24 4:37 Nitin Gupta
2009-08-24 17:33 ` Pekka Enberg
2009-08-24 17:52 ` Nitin Gupta
2009-08-24 18:08 ` Pekka Enberg
2009-08-24 18:11 ` Nitin Gupta
2009-08-24 18:27 ` Pekka Enberg
2009-08-24 18:40 ` Nitin Gupta
2009-08-24 19:36 ` Nitin Gupta
2009-08-24 19:43 ` Pekka Enberg
2009-08-24 21:16 ` Nitin Gupta
2009-08-25 4:26 ` Pekka Enberg
2009-08-24 20:39 ` Hugh Dickins [this message]
2009-08-24 21:16 ` Nitin Gupta
2009-08-24 21:46 ` Hugh Dickins
2009-08-25 14:52 ` Nitin Gupta
2009-08-25 19:03 ` Nitin Gupta
2009-08-26 16:10 ` Christoph Lameter
2009-08-26 16:17 ` Nitin Gupta
2009-08-26 16:19 ` Pekka Enberg
2009-08-26 16:07 ` Christoph Lameter
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