From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759448AbYEMMlM (ORCPT ); Tue, 13 May 2008 08:41:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751606AbYEMMk6 (ORCPT ); Tue, 13 May 2008 08:40:58 -0400 Received: from saeurebad.de ([85.214.36.134]:53700 "EHLO saeurebad.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752299AbYEMMk5 (ORCPT ); Tue, 13 May 2008 08:40:57 -0400 From: Johannes Weiner To: Andi Kleen Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ingo Molnar , Yinghai Lu , Andrew Morton , Linus Torvalds Subject: Re: [PATCH 0/3] bootmem2 III References: <20080509151713.939253437@saeurebad.de> <20080509184044.GA19109@one.firstfloor.org> <87lk2gtzta.fsf@saeurebad.de> <48275493.40601@firstfloor.org> Date: Tue, 13 May 2008 14:40:44 +0200 In-Reply-To: <48275493.40601@firstfloor.org> (Andi Kleen's message of "Sun, 11 May 2008 22:18:27 +0200") Message-ID: <874p92qsvn.fsf@saeurebad.de> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.0.60 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.1.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Andi Kleen writes: > Johannes Weiner wrote: > >>> On Fri, May 09, 2008 at 05:17:13PM +0200, Johannes Weiner wrote: >>>> here is bootmem2, a memory block-oriented boot time allocator. >>>> >>>> Recent NUMA topologies broke the current bootmem's assumption that >>>> memory nodes provide non-overlapping and contiguous ranges of pages. >>> I'm still not sure that's a really good rationale for bootmem2. >>> e.g. the non continuous nodes are really special cases and there tends >>> to be enough memory at the beginning which is enough for boot time >>> use, so for those systems it would be quite reasonably to only >>> put the continuous starts of the nodes into bootmem. >> >> Hm, that would put the logic into arch-code. I have no strong opinion >> about it. > > In fact I suspect the current code will already work like that > implicitely. The aliasing is only a problem for the new "arbitary node > free_bootmem" right? And that alloc_bootmem_node() can not garuantee node-locality which is the much worse part, I think. >>> That said the bootmem code has gotten a little crufty and a clean >>> rewrite might be a good idea. >> >> I agree completely. > > The trouble is just that bootmem is used in early boot and early boot is > very subtle and getting it working over all architectures could be a > challenge. Not wanting to discourage you, but it's not exactly the > easiest part of the kernel to hack on. Bootmem seemed pretty self-contained to me, at least in the beginning. The bad thing is that I can test only the most simple configuration with it. I was wondering yesterday if it would be feasible to enforce contiguousness for nodes. So that arch-code does not create one pgdat for each node but one for each contiguous block. I have not yet looked deeper into it, but I suspect that other mm code has similar problems with nodes spanning other nodes. Hannes