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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 D8D79ECDE5F for ; Mon, 23 Jul 2018 06:29:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 896C220779 for ; Mon, 23 Jul 2018 06:29:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 896C220779 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com 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 S2387907AbeGWH2L (ORCPT ); Mon, 23 Jul 2018 03:28:11 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:45912 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387828AbeGWH2L (ORCPT ); Mon, 23 Jul 2018 03:28:11 -0400 Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w6N6SSH1017690 for ; Mon, 23 Jul 2018 02:28:33 -0400 Received: from e06smtp01.uk.ibm.com (e06smtp01.uk.ibm.com [195.75.94.97]) by mx0a-001b2d01.pphosted.com with ESMTP id 2kd7r4vq0p-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 23 Jul 2018 02:28:33 -0400 Received: from localhost by e06smtp01.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 23 Jul 2018 07:28:27 +0100 Received: from d06av25.portsmouth.uk.ibm.com (d06av25.portsmouth.uk.ibm.com [9.149.105.61]) by b06cxnps3075.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w6N6SQTN38862882 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 23 Jul 2018 06:28:26 GMT Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 36B1911C05C; Mon, 23 Jul 2018 09:28:41 +0100 (BST) Received: from d06av25.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D488B11C04C; Mon, 23 Jul 2018 09:28:38 +0100 (BST) Received: from [9.109.221.92] (unknown [9.109.221.92]) by d06av25.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 23 Jul 2018 09:28:38 +0100 (BST) Subject: Re: [RFC 0/4] Virtio uses DMA API for all devices To: "Michael S. Tsirkin" References: <20180720035941.6844-1-khandual@linux.vnet.ibm.com> <20180720161541-mutt-send-email-mst@kernel.org> Cc: robh@kernel.org, srikar@linux.vnet.ibm.com, aik@ozlabs.ru, jasowang@redhat.com, linuxram@us.ibm.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, hch@infradead.org, paulus@samba.org, joe@perches.com, linuxppc-dev@lists.ozlabs.org, elfring@users.sourceforge.net, haren@linux.vnet.ibm.com, david@gibson.dropbear.id.au From: Anshuman Khandual Date: Mon, 23 Jul 2018 11:58:23 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <20180720161541-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 18072306-4275-0000-0000-0000029C40FC X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18072306-4276-0000-0000-000037A47131 Message-Id: <8f51d2c6-cc0c-9e42-f0fd-a8a33acc8b83@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-07-22_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1807230077 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/20/2018 06:46 PM, Michael S. Tsirkin wrote: > On Fri, Jul 20, 2018 at 09:29:37AM +0530, Anshuman Khandual wrote: >> This patch series is the follow up on the discussions we had before about >> the RFC titled [RFC,V2] virtio: Add platform specific DMA API translation >> for virito devices (https://patchwork.kernel.org/patch/10417371/). There >> were suggestions about doing away with two different paths of transactions >> with the host/QEMU, first being the direct GPA and the other being the DMA >> API based translations. >> >> First patch attempts to create a direct GPA mapping based DMA operations >> structure called 'virtio_direct_dma_ops' with exact same implementation >> of the direct GPA path which virtio core currently has but just wrapped in >> a DMA API format. Virtio core must use 'virtio_direct_dma_ops' instead of >> the arch default in absence of VIRTIO_F_IOMMU_PLATFORM flag to preserve the >> existing semantics. The second patch does exactly that inside the function >> virtio_finalize_features(). The third patch removes the default direct GPA >> path from virtio core forcing it to use DMA API callbacks for all devices. >> Now with that change, every device must have a DMA operations structure >> associated with it. The fourth patch adds an additional hook which gives >> the platform an opportunity to do yet another override if required. This >> platform hook can be used on POWER Ultravisor based protected guests to >> load up SWIOTLB DMA callbacks to do the required (as discussed previously >> in the above mentioned thread how host is allowed to access only parts of >> the guest GPA range) bounce buffering into the shared memory for all I/O >> scatter gather buffers to be consumed on the host side. >> >> Please go through these patches and review whether this approach broadly >> makes sense. I will appreciate suggestions, inputs, comments regarding >> the patches or the approach in general. Thank you. > I like how patches 1-3 look. Could you test performance > with/without to see whether the extra indirection through > use of DMA ops causes a measurable slow-down? I ran this simple DD command 10 times where /dev/vda is a virtio block device of 10GB size. dd if=/dev/zero of=/dev/vda bs=8M count=1024 oflag=direct With and without patches bandwidth which has a bit wide range does not look that different from each other. Without patches =============== ---------- 1 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.95557 s, 4.4 GB/s ---------- 2 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 2.05176 s, 4.2 GB/s ---------- 3 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.88314 s, 4.6 GB/s ---------- 4 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.84899 s, 4.6 GB/s ---------- 5 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 5.37184 s, 1.6 GB/s ---------- 6 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.9205 s, 4.5 GB/s ---------- 7 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 6.85166 s, 1.3 GB/s ---------- 8 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.74049 s, 4.9 GB/s ---------- 9 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 6.31699 s, 1.4 GB/s ---------- 10 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 2.47057 s, 3.5 GB/s With patches ============ ---------- 1 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 2.25993 s, 3.8 GB/s ---------- 2 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.82438 s, 4.7 GB/s ---------- 3 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.93856 s, 4.4 GB/s ---------- 4 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.83405 s, 4.7 GB/s ---------- 5 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 7.50199 s, 1.1 GB/s ---------- 6 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 2.28742 s, 3.8 GB/s ---------- 7 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 5.74958 s, 1.5 GB/s ---------- 8 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.99149 s, 4.3 GB/s ---------- 9 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 5.67647 s, 1.5 GB/s ---------- 10 --------- 1024+0 records in 1024+0 records out 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 2.93957 s, 2.9 GB/s Does this look okay ?