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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 47F49C433EF for ; Thu, 24 Feb 2022 06:33:37 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8DE858D0002; Thu, 24 Feb 2022 01:33:36 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8670F8D0001; Thu, 24 Feb 2022 01:33:36 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 72EE98D0002; Thu, 24 Feb 2022 01:33:36 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0035.hostedemail.com [216.40.44.35]) by kanga.kvack.org (Postfix) with ESMTP id 46EF38D0001 for ; Thu, 24 Feb 2022 01:33:36 -0500 (EST) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id B9B3C9F5DA for ; Thu, 24 Feb 2022 06:33:35 +0000 (UTC) X-FDA: 79176707190.22.5154713 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf23.hostedemail.com (Postfix) with ESMTP id D83E4140002 for ; Thu, 24 Feb 2022 06:33:34 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 3C97768AA6; Thu, 24 Feb 2022 07:33:30 +0100 (CET) Date: Thu, 24 Feb 2022 07:33:30 +0100 From: Christoph Hellwig To: Heiko Carstens Cc: Christoph Hellwig , Baoquan He , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, cl@linux.com, 42.hyeyoo@gmail.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, vbabka@suse.cz, David.Laight@aculab.com, david@redhat.com, herbert@gondor.apana.org.au, davem@davemloft.net, linux-crypto@vger.kernel.org, steffen.klassert@secunet.com, netdev@vger.kernel.org, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, linux-s390@vger.kernel.org, michael@walle.cc, linux-i2c@vger.kernel.org, wsa@kernel.org, Halil Pasic , Vineeth Vijayan Subject: Re: [PATCH 00/22] Don't use kmalloc() with GFP_DMA Message-ID: <20220224063330.GB20383@lst.de> References: <20220219005221.634-1-bhe@redhat.com> <20220222084422.GA6139@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-Rspamd-Queue-Id: D83E4140002 X-Stat-Signature: az8nueyh8prqa89za6s6gd9ceuqmjd1d X-Rspam-User: Authentication-Results: imf23.hostedemail.com; dkim=none; spf=none (imf23.hostedemail.com: domain of hch@lst.de has no SPF policy when checking 213.95.11.211) smtp.mailfrom=hch@lst.de; dmarc=none X-Rspamd-Server: rspam05 X-HE-Tag: 1645684414-287200 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000004, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Feb 23, 2022 at 08:18:08PM +0100, Heiko Carstens wrote: > > The long term goal is to remove ZONE_DMA entirely at least for > > architectures that only use the small 16MB ISA-style one. It can > > then be replaced with for example a CMA area and fall into a movable > > zone. I'd have to prototype this first and see how it applies to the > > s390 case. It might not be worth it and maybe we should replace > > ZONE_DMA and ZONE_DMA32 with a ZONE_LIMITED for those use cases as > > the amount covered tends to not be totally out of line for what we > > built the zone infrastructure. > > So probably I'm missing something; but for small systems where we > would only have ZONE_DMA, how would a CMA area within this zone > improve things? It would not, but more importantly we would not need it at all. The thinking here is really about the nasty 16MB ISA-style zone DMA. a 31-bit something rather different.