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 A1143ECDE5F for ; Mon, 23 Jul 2018 09:08:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5343820846 for ; Mon, 23 Jul 2018 09:08:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5343820846 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.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 S2388125AbeGWKJI (ORCPT ); Mon, 23 Jul 2018 06:09:08 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:36216 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388048AbeGWKJI (ORCPT ); Mon, 23 Jul 2018 06:09:08 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4B255401DEA8; Mon, 23 Jul 2018 09:08:49 +0000 (UTC) Received: from redhat.com (ovpn-120-12.rdu2.redhat.com [10.10.120.12]) by smtp.corp.redhat.com (Postfix) with SMTP id B2B982026D65; Mon, 23 Jul 2018 09:08:43 +0000 (UTC) Date: Mon, 23 Jul 2018 12:08:42 +0300 From: "Michael S. Tsirkin" To: Anshuman Khandual 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 Subject: Re: [RFC 0/4] Virtio uses DMA API for all devices Message-ID: <20180723120511-mutt-send-email-mst@kernel.org> References: <20180720035941.6844-1-khandual@linux.vnet.ibm.com> <20180720161541-mutt-send-email-mst@kernel.org> <8f51d2c6-cc0c-9e42-f0fd-a8a33acc8b83@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8f51d2c6-cc0c-9e42-f0fd-a8a33acc8b83@linux.vnet.ibm.com> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Mon, 23 Jul 2018 09:08:54 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Mon, 23 Jul 2018 09:08:54 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'mst@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 23, 2018 at 11:58:23AM +0530, Anshuman Khandual wrote: > 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 ? You want to test IOPS with lots of small writes and using raw ramdisk on host. -- MST