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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 756CBC43610 for ; Tue, 20 Nov 2018 09:20:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3F14F2146D for ; Tue, 20 Nov 2018 09:20:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3F14F2146D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727010AbeKTTsS (ORCPT ); Tue, 20 Nov 2018 14:48:18 -0500 Received: from verein.lst.de ([213.95.11.211]:43936 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726477AbeKTTsS (ORCPT ); Tue, 20 Nov 2018 14:48:18 -0500 Received: by newverein.lst.de (Postfix, from userid 2407) id F18C568B02; Tue, 20 Nov 2018 10:20:10 +0100 (CET) Date: Tue, 20 Nov 2018 10:20:10 +0100 From: Christoph Hellwig To: Nicolin Chen Cc: Christoph Hellwig , Robin Murphy , m.szyprowski@samsung.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, vdumpa@nvidia.com Subject: Re: [PATCH RFC] dma-direct: do not allocate a single page from CMA area Message-ID: <20181120092010.GA7270@lst.de> References: <20181031200355.19945-1-nicoleotsuka@gmail.com> <13d60076-33ad-b542-4d17-4d717d5aa4d3@arm.com> <20181102063542.GA17073@lst.de> <20181105224050.GA10411@Asurada-Nvidia.nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181105224050.GA10411@Asurada-Nvidia.nvidia.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 05, 2018 at 02:40:51PM -0800, Nicolin Chen wrote: > > > In general, this seems to make sense to me. It does represent a theoretical > > > change in behaviour for devices which have their own CMA area somewhere > > > other than kernel memory, and only ever make non-atomic allocations, but > > > I'm not sure whether that's a realistic or common enough case to really > > > worry about. > > > > Yes, I think we should make the decision in dma_alloc_from_contiguous > > based on having a per-dev CMA area or not. There is a lot of cruft in > > It seems that cma_alloc() already has a CMA area check? Would it > be duplicated to have a similar one in dma_alloc_from_contiguous? It isn't duplicate if it serves a different purpose. > > this area that should be cleaned up while we're at it, like always > > falling back to the normal page allocator if there is no CMA area or > > nothing suitable found in dma_alloc_from_contiguous instead of > > having to duplicate all that in the caller. > > Am I supposed to clean up things that's mentioned above by moving > the fallback allocator into dma_alloc_from_contiguous, or to just > move my change (the count check) into dma_alloc_from_contiguous? > > I understand that'd be great to have a cleanup, yet feel it could > be done separately as this patch isn't really a cleanup change. I can take care of any cleanups. I've been trying to dust up that area anyway.