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 4FB2CC41513 for ; Wed, 26 Jul 2023 07:57:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232986AbjGZH5f (ORCPT ); Wed, 26 Jul 2023 03:57:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47272 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231329AbjGZH45 (ORCPT ); Wed, 26 Jul 2023 03:56:57 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9E96F7299 for ; Wed, 26 Jul 2023 00:49:19 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 2A53921D5C; Wed, 26 Jul 2023 07:49:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1690357753; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=GONJa8tzUwqKA0Fz+wB3U1k6lRkAIjy3GSK0vW8uCcE=; b=joabLHJaqcBy5EOkcJ/+cXWbBd5JWYFFbiCuer3a/tc7fWHsOeV8TEvKSuciFuNDUBiJ6W K1lWHyWK28xzic4hIpByu5BwKQhKgITs56ZfTAF5OlP9c1v3b+qUR3Qqt++Fwd87LBqgjv DkBqFo4aQVUb02Kv1ckXdQQJHrgUOlM= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 0C0341341F; Wed, 26 Jul 2023 07:49:13 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id EPN5APnPwGTrMAAAMHmgww (envelope-from ); Wed, 26 Jul 2023 07:49:13 +0000 Date: Wed, 26 Jul 2023 09:49:12 +0200 From: Michal Hocko To: Mike Rapoport 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: References: <20230718220106.GA3117638@google.com> <20230719054434.GG1901145@kernel.org> <20230719222604.GB3528218@google.com> <20230721112009.GP1901145@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230721112009.GP1901145@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri 21-07-23 14:20:09, Mike Rapoport wrote: > On Wed, Jul 19, 2023 at 04:26:04PM -0600, Ross Zwisler wrote: > > On Wed, Jul 19, 2023 at 08:44:34AM +0300, Mike Rapoport wrote: > > > 3. Switch memblock to use bottom up allocations. Historically memblock > > > allocated memory from the top to avoid corrupting the kernel image and to > > > avoid exhausting precious ZONE_DMA. I believe we can use bottom-up > > > allocations with lower limit of memblock allocations set to 16M. > > > > > > With the hack below no memblock allocations will end up in ZONE_MOVABLE: > > > > Yep, I've confirmed that for my use cases at least this does the trick, thank > > you! I had thought about moving the memblock allocations, but had no idea it > > was (basically) already supported and thought it'd be much riskier than just > > adjusting where ZONE_MOVABLE lived. > > > > Is there a reason for this to not be a real option for users, maybe per a > > kernel config knob or something? I'm happy to explore other options in this > > thread, but this is doing the trick so far. > > I think we can make x86 always use bottom up. > > To do this properly we'd need to set lower limit for memblock allocations > to MAX_DMA32_PFN and allow fallback below it so that early allocations > won't eat memory from ZONE_DMA32. > > Aside from x86 boot being fragile in general I don't see why this wouldn't > work. This would add a very subtle depency of a functionality on the specific boot allocator behavior and that is bad for long term maintenance. -- Michal Hocko SUSE Labs