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=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 A29D8C31E4C for ; Fri, 14 Jun 2019 15:01:30 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 82DCD21537 for ; Fri, 14 Jun 2019 15:01:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 82DCD21537 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ACULAB.COM Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 686ACFF7; Fri, 14 Jun 2019 15:01:30 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 0B85CF45 for ; Fri, 14 Jun 2019 15:01:29 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [207.82.80.151]) by smtp1.linuxfoundation.org (Postfix) with ESMTP id 4E009E5 for ; Fri, 14 Jun 2019 15:01:28 +0000 (UTC) Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-6-Ae-vvi9EMKOPr28p6sbQQA-1; Fri, 14 Jun 2019 16:01:23 +0100 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b::d117) by AcuMS.aculab.com (fd9f:af1c:a25b::d117) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Fri, 14 Jun 2019 16:01:22 +0100 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Fri, 14 Jun 2019 16:01:22 +0100 From: David Laight To: 'Christoph Hellwig' Subject: RE: [PATCH 16/16] dma-mapping: use exact allocation in dma_alloc_contiguous Thread-Topic: [PATCH 16/16] dma-mapping: use exact allocation in dma_alloc_contiguous Thread-Index: AQHVIrfpTFjppS25RkWUhwqPPyqZ4qabLzdw///7eICAABIeYA== Date: Fri, 14 Jun 2019 15:01:22 +0000 Message-ID: References: <20190614134726.3827-1-hch@lst.de> <20190614134726.3827-17-hch@lst.de> <20190614145001.GB9088@lst.de> In-Reply-To: <20190614145001.GB9088@lst.de> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-MC-Unique: Ae-vvi9EMKOPr28p6sbQQA-1 X-Mimecast-Spam-Score: 0 Cc: Maxime Ripard , Joonas Lahtinen , "dri-devel@lists.freedesktop.org" , "linux-mm@kvack.org" , "devel@driverdev.osuosl.org" , "linux-s390@vger.kernel.org" , "linux-rdma@vger.kernel.org" , David Airlie , "linux-media@vger.kernel.org" , Intel Linux Wireless , "intel-gfx@lists.freedesktop.org" , Maarten Lankhorst , Jani Nikula , Ian Abbott , Rodrigo Vivi , Sean Paul , "moderated list:ARM PORT" , "netdev@vger.kernel.org" , "linux-wireless@vger.kernel.org" , "linux-kernel@vger.kernel.org" , H Hartley Sweeten , "iommu@lists.linux-foundation.org" , Daniel Vetter X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org From: 'Christoph Hellwig' > Sent: 14 June 2019 15:50 > To: David Laight > On Fri, Jun 14, 2019 at 02:15:44PM +0000, David Laight wrote: > > Does this still guarantee that requests for 16k will not cross a 16k boundary? > > It looks like you are losing the alignment parameter. > > The DMA API never gave you alignment guarantees to start with, > and you can get not naturally aligned memory from many of our > current implementations. Hmmm... I thought that was even documented. I'm pretty sure there is a lot of code out there that makes that assumption. Without it many drivers will have to allocate almost double the amount of memory they actually need in order to get the required alignment. So instead of saving memory you'll actually make more be used. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu