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From: Christoph Lameter <cl@linux-foundation.org>
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: Wed, 26 Aug 2009 12:07:47 -0400 (EDT)	[thread overview]
Message-ID: <alpine.DEB.1.10.0908261204400.9933@gentwo.org> (raw)
In-Reply-To: <4A92EBB4.1070101@vflare.org>

On Tue, 25 Aug 2009, Nitin Gupta wrote:

> PFNs are 32-bit on all archs while for 'struct page *', we require 32-bit or
> 64-bit depending on arch. ramzswap allocates a table entry <pagenum, offset>
> corresponding to every swap slot. So, the size of table will unnecessarily
> increase on 64-bit archs. Same is the argument for xvmalloc free list sizes.

Wrong. PFNs must be longer than 32 bit otherwise a system cannot
address more than 2^12 + 2^32 = 2^44 =>  16TB.

The type used for PFNs is unsigned long which are 64 bit on 64 bit platforms.

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      parent reply	other threads:[~2009-08-26 16:08 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
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 [this message]

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