From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762806AbYDXTcp (ORCPT ); Thu, 24 Apr 2008 15:32:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761436AbYDXTc3 (ORCPT ); Thu, 24 Apr 2008 15:32:29 -0400 Received: from de01egw01.freescale.net ([192.88.165.102]:61849 "EHLO de01egw01.freescale.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760380AbYDXTc2 (ORCPT ); Thu, 24 Apr 2008 15:32:28 -0400 Message-ID: <4810E033.4090903@freescale.com> Date: Thu, 24 Apr 2008 14:32:03 -0500 From: Timur Tabi User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.8.1.13) Gecko/20080313 SeaMonkey/1.1.9 MIME-Version: 1.0 To: Andi Kleen CC: lkml Subject: Re: Calling free_pages on part of the memory returned by get_free_pages? References: <480D032E.20204@freescale.com> <87r6cvxdd4.fsf@basil.nowhere.org> In-Reply-To: <87r6cvxdd4.fsf@basil.nowhere.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andi Kleen wrote: > It is ok, as long as you don't use compound pages (__GFP_COMP) and call > split_page() to fix up the reference counts. Thanks. I've never even heard of compound pages, so that's not a problem. I'll look up split_page(). > Also you do this to save memory right? Yes, I expect to allocate a 5MB chunk of memory, which means I'll be wasting 3MB of physically-contiguous memory on an embedded system. > The large system hash code does it too Ah, I see that in alloc_large_system_hash(). Thanks > If it's reasonably common we should re-add alloc/get_pages_exact() helper to > make this pattern clear and easier to use. I'd be in favor of that! I was planning on doing something like that anyway. -- Timur Tabi Linux kernel developer at Freescale