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 4F8CFA0352; Mon, 18 Nov 2019 02:37:51 +0100 (CET) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id B7B65F04; Mon, 18 Nov 2019 02:37:50 +0100 (CET) Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by dpdk.org (Postfix) with ESMTP id 18186B62 for ; Mon, 18 Nov 2019 02:37:47 +0100 (CET) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 17 Nov 2019 17:37:47 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,318,1569308400"; d="scan'208";a="195975954" Received: from npg-dpdk-yinanwang.sh.intel.com ([10.67.118.227]) by orsmga007.jf.intel.com with ESMTP; 17 Nov 2019 17:37:45 -0800 From: Yinan To: dev@dpdk.org, maxime.coquelin@redhat.com, tiwei.bie@intel.com Cc: zhihong.wang@intel.com, john.mcnamara@intel.com, marko.kovacevic@intel.com, Yinan Wang Date: Mon, 18 Nov 2019 05:29:23 -0500 Message-Id: <20191118102923.9302-1-yinan.wang@intel.com> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: [dpdk-dev] [PATCH] doc: clarify virtio PMD path selection 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" From: Yinan Wang add virtio paths selection and usage introduction for better virtio usability. Signed-off-by: Yinan Wang --- .../virtio_paths_selection_and_usage.rst | 130 ++++++++++++++++++ 1 file changed, 130 insertions(+) create mode 100644 doc/guides/howto/virtio_paths_selection_and_usage.rst diff --git a/doc/guides/howto/virtio_paths_selection_and_usage.rst b/doc/guides/howto/virtio_paths_selection_and_usage.rst new file mode 100644 index 000000000..b5918eaf9 --- /dev/null +++ b/doc/guides/howto/virtio_paths_selection_and_usage.rst @@ -0,0 +1,130 @@ +.. SPDX-License-Identifier: BSD-3-Clause + Copyright(c) 2019 Intel Corporation. + +Virtio paths Selection and Usage +================================ + +Logically virtio-PMD has 9 paths based on the virtio features (Rx mergeable,In-order,Packed virtqueue) +combinations, below are introduction of virtio three common features: + +* Rx mergeable: With this feature negotiated, device can receive larger packets by combining + individual descriptors. +* In-order: Some devices always use descriptors in the same order in which they have been made + available, these devices can offer the VIRTIO_F_IN_ORDER feature. If this feature negotiated, + driver will use descriptors in order. Meanwhile, this knowledge allows device operate used ring + in batches and driver operate available ring in batches and such can decrease cache miss rate. +* Packed virtqueue: The structure of packed virtqueue is different from split virtqueue，split + virtqueue is composed of available ring, used ring and descriptor table, while packed virtqueue + is composed of descriptor ring，driver event suppression and device event suppression. The idea + behind this is to improve performance by avoiding cache misses and and make it easier for devices + to implement. + +Virtio paths Selection +---------------------- + +If packed virtqueue is not negotiated, below split virtqueue paths can be selected +according to below configuration: + +#. Split virtqueue mergeable path: If Rx mergeable is negotiated, in-order feature is + not negotiated, this path will be selected. +#. Split virtqueue non-mergeable path: If Rx mergeable and in-order feature are not + negotiated, also Rx offload(s) are requested, this path can be selected. +#. Split virtqueue in-order mergeable path: If in-order feature and Rx mergeable are + both negotiated, this path can be selected. +#. Split virtqueue in-order non-mergeable path: If in-order feature is negotiated and + Rx mergeable is not negotiated, this path can be selected. +#. Split virtqueue vectorized RX path: If Rx mergeable is disabled and no Rx offload + requested, this path can be selected. + +If packed virtqueue is negotiated, below packed virtqueue paths can be selected +according to below configuration: + +#. Packed virtqueue mergeable path: If Rx mergeable is negotiated, in-order feature + is not negotiated, this path will be selected. +#. Packed virtqueue non-mergeable path: If Rx mergeable and in-order feature are not + negotiated, also Rx offload(s) are requested, this path will be selected. +#. Packed virtqueue in-order mergeable path: If in-order feature and Rx mergeable are + both negotiated, this path will be selected. +#. Packed virtqueue in-order non-mergeable path: If in-order feature is negotiated and + Rx mergeable is not negotiated, this path will be selected. + +Rx/Tx callbacks of each Virtio path +----------------------------------- + +Refer to above descriptions,virtio path and Rx/TX callbacks are auto selected by different parameters of +vdev and workloads. Rx callbacks and Tx callbacks name for each Virtio Path are shown in following tables:: + + +----------------------------------------------------------------------------------------------------------+ + | Virtio path | Rx callbacks | TX callbacks | + +----------------------------------------------------------------------------------------------------------+ + |Split virtqueue mergeable path |virtio_recv_mergeable_pkts | virtio_xmit_pkts | + +----------------------------------------------------------------------------------------------------------+ + |Split virtqueue non-mergeable path | virtio_recv_pkts | virtio_xmit_pkts | + +----------------------------------------------------------------------------------------------------------+ + |Split virtqueue in-order mergeable path | virtio_recv_pkts_inorder | virtio_xmit_pkts_inorder| + +----------------------------------------------------------------------------------------------------------+ + |Split virtqueue in-order non-mergeable path | virtio_recv_pkts_inorder | virtio_xmit_pkts_inorder| + +----------------------------------------------------------------------------------------------------------+ + |Split virtqueue vectorized RX path | virtio_recv_pkts_vec | virtio_xmit_pkts | + +----------------------------------------------------------------------------------------------------------+ + |Packed virtqueue mergeable path | virtio_recv_mergeable_pkts_packed| virtio_xmit_pkts_packed | + +----------------------------------------------------------------------------------------------------------+ + |Packed virtqueue normal path | virtio_recv_pkts_packed | virtio_xmit_pkts_packed | + +----------------------------------------------------------------------------------------------------------+ + |Packed virtqueue in-order mergeable path | virtio_recv_mergeable_pkts_packed| virtio_xmit_pkts_packed | + +----------------------------------------------------------------------------------------------------------+ + |Packed virtqueue in-order normal path | virtio_recv_pkts_packed | virtio_xmit_pkts_packed | + +----------------------------------------------------------------------------------------------------------+ + +Virtio paths Support Status from Release to Release +--------------------------------------------------- + +Virtio feature implementation: + +* In-order feature implemented in DPDK 18.08 by adding new Rx/TX callbacks + ``virtio_recv_pkts_inorder`` and ``virtio_xmit_pkts_inorder``. +* Packed virtqueue implemented in DPDK 19.02 by adding new Rx/TX callbacks + ``virtio_recv_pkts_packed`` , ``virtio_recv_mergeable_pkts_packed`` and ``virtio_xmit_pkts_packed``. + +Virtio path number changes from release to release, all virtio paths support status are shown in below table:: + + +--------------------------------------------------------------------------------------------------------------------------------------------------------+ + |Virtio path\ DPDK version | v16.11 | v17.02 | v17.05 | v17.08 | v17.11 | v18.02 | v18.05 | v18.08 | v18.11 | v19.02 | v19.05 | v19.08 | + +--------------------------------------------------------------------------------------------------------------------------------------------------------+ + |Split virtqueue mergebale path | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | + +--------------------------------------------------------------------------------------------------------------------------------------------------------+ + |Split virtqueue non-mergeable path | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | + +--------------------------------------------------------------------------------------------------------------------------------------------------------+ + |Split virtqueue vectorized RX path | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | Y | + ---------------------------------------------------------------------------------------------------------------------------------------------------------+ + |Split virtqueue simple TX path | Y | Y | Y | Y | Y | Y | Y | N | N | N | N | N | + ---------------------------------------------------------------------------------------------------------------------------------------------------------+ + |Split virtqueue in-order non-mergeable path | | | | | | | | Y | Y | Y | Y | Y | + ---------------------------------------------------------------------------------------------------------------------------------------------------------+ + |Split virtqueue in-order mergeable path | | | | | | | | Y | Y | Y | Y | Y | + ---------------------------------------------------------------------------------------------------------------------------------------------------------+ + |Packed virtqueue mergeable path | | | | | | | | | | Y | Y | Y | + ---------------------------------------------------------------------------------------------------------------------------------------------------------+ + |Packed virtqueue non-mergeable path | | | | | | | | | | Y | Y | Y | + ---------------------------------------------------------------------------------------------------------------------------------------------------------+ + |Packed virtqueue in-order mergeable path | | | | | | | | | | Y | Y | Y | + ---------------------------------------------------------------------------------------------------------------------------------------------------------+ + |Packed virtqueue in-order non-mergeable path| | | | | | | | | | Y | Y | Y | + ---------------------------------------------------------------------------------------------------------------------------------------------------------+ + +QEMU Support Status +------------------- + +Qemu only support three path of Virtio-PMD: Split virtqueue mergebale path, +Split virtqueue no-mergeable path，Split virtqueue vectorized RX path. + +How to Debug +------------ + +If you meet performance drop or some other issues after upgrading the driver +or configuration, below steps can help you identify which path you selected and +root cause faster. + +#. Run vhost/virtio test case; +#. Run "perf top" and check virtio Rx/tx callback names; +#. Identify which virtio path is selected refer to above table. -- 2.17.1