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 2B73EA04C2; Mon, 25 Nov 2019 16:52:11 +0100 (CET) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id F084D2952; Mon, 25 Nov 2019 16:52:10 +0100 (CET) Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by dpdk.org (Postfix) with ESMTP id 61F0CA3 for ; Mon, 25 Nov 2019 16:52:09 +0100 (CET) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Nov 2019 07:52:08 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,242,1571727600"; d="scan'208";a="206177896" Received: from npg-dpdk-yinanwang.sh.intel.com ([10.67.118.227]) by fmsmga008.fm.intel.com with ESMTP; 25 Nov 2019 07:52:06 -0800 From: Yinan To: dev@dpdk.org, maxime.coquelin@redhat.com, tiwei.bie@intel.com Cc: john.mcnamara@intel.com, zhihong.wang@intel.com, Wang Yinan Date: Mon, 25 Nov 2019 19:43:39 -0500 Message-Id: <20191126004339.22208-1-yinan.wang@intel.com> X-Mailer: git-send-email 2.17.1 Subject: [dpdk-dev] [PATCH v2] 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: Wang Yinan add virtio paths selection and usage introduction for better virtio usability. Signed-off-by: Wang Yinan --- .../virtio_paths_selection_and_usage.rst | 142 ++++++++++++++++++ 1 file changed, 142 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..f51741609 --- /dev/null +++ b/doc/guides/howto/virtio_paths_selection_and_usage.rst @@ -0,0 +1,142 @@ +.. 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 now support three path of split virtqueue: Split virtqueue mergebale path, + Split virtqueue no-mergeable path, Split virtqueue vectorized RX path. +* Since qemu 4.2.0, Packed virtqueue mergeable path and Packed virtqueue non-mergeable + path can be supported. + +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