From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 21B64A2EDB for ; Fri, 6 Sep 2019 15:21:49 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id DCC841F3C8; Fri, 6 Sep 2019 15:21:48 +0200 (CEST) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id 698CA1BFED for ; Fri, 6 Sep 2019 15:21:47 +0200 (CEST) Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id CF0CD301D67F; Fri, 6 Sep 2019 13:21:46 +0000 (UTC) Received: from [10.36.112.25] (ovpn-112-25.ams2.redhat.com [10.36.112.25]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 51B1A60F88; Fri, 6 Sep 2019 13:21:45 +0000 (UTC) To: Tiwei Bie , zhihong.wang@intel.com, john.mcnamara@intel.com, marko.kovacevic@intel.com, dev@dpdk.org References: <20190813020730.10038-1-tiwei.bie@intel.com> <20190813020730.10038-6-tiwei.bie@intel.com> From: Maxime Coquelin Openpgp: preference=signencrypt Autocrypt: addr=maxime.coquelin@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190813020730.10038-6-tiwei.bie@intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.47]); Fri, 06 Sep 2019 13:21:46 +0000 (UTC) Subject: Re: [dpdk-dev] [PATCH 5/6] doc: document packed virtqueue for virtio X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 8/13/19 4:07 AM, Tiwei Bie wrote: > Document the packed virtqueue layout support in virtio net PMD. > > Signed-off-by: Tiwei Bie > --- > doc/guides/nics/virtio.rst | 63 ++++++++++++++++++++++++++++---------- > 1 file changed, 47 insertions(+), 16 deletions(-) > > diff --git a/doc/guides/nics/virtio.rst b/doc/guides/nics/virtio.rst > index 993e691f5..011954ff6 100644 > --- a/doc/guides/nics/virtio.rst > +++ b/doc/guides/nics/virtio.rst > @@ -24,15 +24,19 @@ standard qemu vhost back end and vhost kni back end. > Virtio Implementation in DPDK > ----------------------------- > > -For details about the virtio spec, refer to Virtio PCI Card Specification written by Rusty Russell. > +For details about the virtio spec, refer to the latest > +`VIRTIO (Virtual I/O) Device Specification > +`_. > > -As a PMD, virtio provides packet reception and transmission callbacks virtio_recv_pkts and virtio_xmit_pkts. > +As a PMD, virtio provides packet reception and transmission callbacks. > > -In virtio_recv_pkts, index in range [vq->vq_used_cons_idx , vq->vq_ring.used->idx) in vring is available for virtio to burst out. > +In Rx, packets described by the used descriptors in vring are available > +for virtio to burst out. > > -In virtio_xmit_pkts, same index range in vring is available for virtio to clean. > -Virtio will enqueue to be transmitted packets into vring, advance the vq->vq_ring.avail->idx, > -and then notify the host back end if necessary. > +In Tx, packets described by the used descriptors in vring are available > +for virtio to clean. Virtio will enqueue to be transmitted packets into > +vring, make them available to the device, and then notify the host back > +end if necessary. > > Features and Limitations of virtio PMD > -------------------------------------- > @@ -201,37 +205,52 @@ The packet transmission flow is: > Virtio PMD Rx/Tx Callbacks > -------------------------- > > -Virtio driver has 4 Rx callbacks and 2 Tx callbacks. > +Virtio driver has 6 Rx callbacks and 3 Tx callbacks. > > Rx callbacks: > > #. ``virtio_recv_pkts``: > - Regular version without mergeable Rx buffer support. > + Regular version without mergeable Rx buffer support for split virtqueue. > > #. ``virtio_recv_mergeable_pkts``: > - Regular version with mergeable Rx buffer support. > + Regular version with mergeable Rx buffer support for split virtqueue. > > #. ``virtio_recv_pkts_vec``: > Vector version without mergeable Rx buffer support, also fixes the available > - ring indexes and uses vector instructions to optimize performance. > + ring indexes and uses vector instructions to optimize performance for split > + virtqueue. > > #. ``virtio_recv_pkts_inorder``: > - In-order version with mergeable and non-mergeable Rx buffer support. > + In-order version with mergeable and non-mergeable Rx buffer support > + for split virtqueue. > + > +#. ``virtio_recv_pkts_packed``: > + Regular and in-order version without mergeable Rx buffer support for > + packed virtqueue. > + > +#. ``virtio_recv_mergeable_pkts_packed``: > + Regular and in-order version with mergeable Rx buffer support for packed > + virtqueue. > > Tx callbacks: > > #. ``virtio_xmit_pkts``: > - Regular version. > + Regular version for split virtqueue. > > #. ``virtio_xmit_pkts_inorder``: > - In-order version. > + In-order version for split virtqueue. > + > +#. ``virtio_xmit_pkts_packed``: > + Regular and in-order version for packed virtqueue. > > By default, the non-vector callbacks are used: > > -* For Rx: If mergeable Rx buffers is disabled then ``virtio_recv_pkts`` is > - used; otherwise ``virtio_recv_mergeable_pkts``. > +* For Rx: If mergeable Rx buffers is disabled then ``virtio_recv_pkts`` > + or ``virtio_recv_pkts_packed`` will be used, otherwise > + ``virtio_recv_mergeable_pkts`` or ``virtio_recv_mergeable_pkts_packed`` > + will be used. > > -* For Tx: ``virtio_xmit_pkts``. > +* For Tx: ``virtio_xmit_pkts`` or ``virtio_xmit_pkts_packed`` will be used. > > > Vector callbacks will be used when: > @@ -242,6 +261,8 @@ The corresponding callbacks are: > > * For Rx: ``virtio_recv_pkts_vec``. > > +There is no vector callbacks for packed virtqueue for now. > + > > Example of using the vector version of the virtio poll mode driver in > ``testpmd``:: > @@ -250,10 +271,15 @@ Example of using the vector version of the virtio poll mode driver in > > In-order callbacks only work on simulated virtio user vdev. > > +For split virtqueue: > + > * For Rx: If in-order is enabled then ``virtio_recv_pkts_inorder`` is used. > > * For Tx: If in-order is enabled then ``virtio_xmit_pkts_inorder`` is used. > > +For packed virtqueue, the default callbacks already support the > +in-order feature. > + > Interrupt mode > -------------- > > @@ -372,3 +398,8 @@ Below devargs are supported by the virtio-user vdev: > > It is used to enable virtio device in-order feature. > (Default: 1 (enabled)) > + > +#. ``packed_vq``: > + > + It is used to enable virtio device packed virtqueue feature. > + (Default: 0 (disabled)) > Side note: One day, we may consider to enable it by default. Reviewed-by: Maxime Coquelin