From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754338Ab0CXJAt (ORCPT ); Wed, 24 Mar 2010 05:00:49 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:56365 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753327Ab0CXJAq (ORCPT ); Wed, 24 Mar 2010 05:00:46 -0400 Date: Wed, 24 Mar 2010 10:00:31 +0100 From: Ingo Molnar To: Benjamin Herrenschmidt Cc: Yinghai Lu , Thomas Gleixner , David Miller , Andrew Morton , Linus Torvalds , hpa@zytor.com, jbarnes@virtuousgeek.org, ebiederm@xmission.com, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: [PATCH 06/20] early_res: seperate common memmap func from e820.c to fw_memmap.cy Message-ID: <20100324090031.GA23804@elte.hu> References: <4BA80019.5000900@kernel.org> <4BA813A4.1010704@kernel.org> <4BA8594F.8090205@kernel.org> <20100323080252.GA4848@elte.hu> <4BA883C0.2070102@kernel.org> <20100323094834.GB4576@elte.hu> <1269404982.8599.148.camel@pasglop> <1269405882.8599.155.camel@pasglop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1269405882.8599.155.camel@pasglop> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Benjamin Herrenschmidt wrote: > > > I though one possibility would be to have LMB regions become more lists > > than arrays, so that the static storage only needs to cover as much as > > is needed during really early boot (and we could probably still move the > > BSS top point on some archs to dynamically make more ... actually we > > could be smart arses and use LMB to allocate more LMB list heads if we > > are reaching the table limit :-) > > Actually what about that: > > LMB entries are linked-listed. The array is just storage for those entry > "heads". > > The initial static array only needs to be big enough for very very early > platform specific kernel bits and pieces, so it could even be sized by a > Kconfig option. Or it could just use a klimit moving trick to pick up a > page right after the BSS but that may need to be arch specific. > > lmb_init() queues all the entries from the initial array in a freelist > > lmb_alloc() and lmb_reserve() just pop entries from that freelist to > populate the two main linked lists (memory and reserved). > > When something tries to dequeue up the last freelist entry, then under > the hood, LMB uses it instead to allocate a new block of LMB entries > that gets added to the freelist. > > We never free blocks of LMB entries. > > That way, we can fine tine the static array to be as small as we can > realistically make it be, and we have no boundary limitations on the > amount of entries in either the memory list or the reserved list. > > I'm a bit too flat out right now to write code, but if there's no objection, > I might give that a go either later this week or next week, see if I can > replace bootmem on powerpc. That would be fantastic! PowerPC and x86 both doing it would give it enough of a critical mass to make the removal of bootmem realistic. Thanks, Ingo