From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 47205C0015E for ; Wed, 19 Jul 2023 08:00:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229983AbjGSIAU (ORCPT ); Wed, 19 Jul 2023 04:00:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49786 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229536AbjGSIAS (ORCPT ); Wed, 19 Jul 2023 04:00:18 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 61E989D for ; Wed, 19 Jul 2023 01:00:17 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id ED5EA612E1 for ; Wed, 19 Jul 2023 08:00:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 49482C433C8; Wed, 19 Jul 2023 08:00:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689753616; bh=NTb4KuKKWr4nc9YdxvCXJe6mrt/xu9Zh8G0AeS4XV4w=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JkDmlNul1ZIiLTrknFa35/tFU8UA4MAK9oBy4J9L/GcA7AU/vugIuFM4V1xVAjCrB suEHTw8Itt8Z6YtWAh03Xc3fuMufsLVMfNp34se3oOcgdObERDMTT4cyY0RThVwvZC 29FT00hI+c0JvnGs/smwONyn3Vq/8tZRmhukMyLb7kRtE03PyW7B5Lb5jBY9nuFGyS pLOCEveAyWuJ/SZ/DK7B0B6BlFLjuaM81AZ2Cs4bB09dErIlmAtyEcgxSpd32+UY1F VPNoiPmlPiKeoIc6TneN0PUiiOczjUge+g9v8x8tzM3GPu85tB4I8MdurTRf0vVebm /Dom2D/x4X9Qw== Date: Wed, 19 Jul 2023 10:59:52 +0300 From: Mike Rapoport To: Michal Hocko Cc: Ross Zwisler , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Mel Gorman , Vlastimil Babka , David Hildenbrand Subject: Re: collision between ZONE_MOVABLE and memblock allocations Message-ID: <20230719075952.GH1901145@kernel.org> References: <20230718220106.GA3117638@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 19, 2023 at 08:14:48AM +0200, Michal Hocko wrote: > On Tue 18-07-23 16:01:06, Ross Zwisler wrote: > [...] > > I do think that we need to fix this collision between ZONE_MOVABLE and memmap > > allocations, because this issue essentially makes the movablecore= kernel > > command line parameter useless in many cases, as the ZONE_MOVABLE region it > > creates will often actually be unmovable. > > movablecore is kinda hack and I would be more inclined to get rid of it > rather than build more into it. Could you be more specific about your > use case? > > > Here are the options I currently see for resolution: > > > > 1. Change the way ZONE_MOVABLE memory is allocated so that it is allocated from > > the beginning of the NUMA node instead of the end. This should fix my use case, > > but again is prone to breakage in other configurations (# of NUMA nodes, other > > architectures) where ZONE_MOVABLE and memblock allocations might overlap. I > > think that this should be relatively straightforward and low risk, though. > > > > 2. Make the code which processes the movablecore= command line option aware of > > the memblock allocations, and have it choose a region for ZONE_MOVABLE which > > does not have these allocations. This might be done by checking for > > PageReserved() as we do with offlining memory, though that will take some boot > > time reordering, or we'll have to figure out the overlap in another way. This > > may also result in us having two ZONE_NORMAL zones for a given NUMA node, with > > a ZONE_MOVABLE section in between them. I'm not sure if this is allowed? > > Yes, this is no problem. Zones are allowed to be sparse. The current initialization order is roughly * very early initialization with some memblock allocations * determine zone locations and sizes * initialize memory map - memblock_alloc(lots of memory) * lots of unrelated initializations that may allocate memory * release free pages from memblock to the buddy allocator With 2) we can make sure the memory map and early allocations won't be in the ZONE_MOVABLE, but we'll still may have reserved pages there. > > If > > we can get it working, this seems like the most correct solution to me, but > > also the most difficult and risky because it involves significant changes in > > the code for memory setup at early boot. > > > > Am I missing anything are there other solutions we should consider, or do you > > have an opinion on which solution we should pursue? > > If this really needs to be addressed than 2) is certainly a more robust > approach. > -- > Michal Hocko > SUSE Labs -- Sincerely yours, Mike.