From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751568AbZHZQIO (ORCPT ); Wed, 26 Aug 2009 12:08:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751255AbZHZQIN (ORCPT ); Wed, 26 Aug 2009 12:08:13 -0400 Received: from smtp4.ultrahosting.com ([74.213.175.253]:38856 "EHLO smtp.ultrahosting.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751140AbZHZQIN (ORCPT ); Wed, 26 Aug 2009 12:08:13 -0400 Date: Wed, 26 Aug 2009 12:07:47 -0400 (EDT) From: Christoph Lameter X-X-Sender: cl@gentwo.org To: Nitin Gupta cc: Pekka Enberg , 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 In-Reply-To: <4A92EBB4.1070101@vflare.org> Message-ID: References: <200908241007.47910.ngupta@vflare.org> <84144f020908241033l4af09e7h9caac47d8d9b7841@mail.gmail.com> <4A92EBB4.1070101@vflare.org> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.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 > 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.