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 9B4EFA04E0; Wed, 27 Nov 2019 07:28:37 +0100 (CET) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 337D15B32; Wed, 27 Nov 2019 07:28:36 +0100 (CET) Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by dpdk.org (Postfix) with ESMTP id 4FE5C235 for ; Wed, 27 Nov 2019 07:28:34 +0100 (CET) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Nov 2019 22:28:33 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,248,1571727600"; d="scan'208";a="211592326" Received: from npg-dpdk-yinanwang.sh.intel.com ([10.67.118.227]) by orsmga003.jf.intel.com with ESMTP; 26 Nov 2019 22:28:31 -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: Wed, 27 Nov 2019 10:19:52 -0500 Message-Id: <20191127151952.7770-1-yinan.wang@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20191118102923.9302-1-yinan.wang@intel.com> References: <20191118102923.9302-1-yinan.wang@intel.com> Subject: [dpdk-dev] [PATCH v5] 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 --- doc/guides/howto/index.rst | 1 + .../virtio_paths_selection_and_usage.rst | 126 ++++++++++++++++++ 2 files changed, 127 insertions(+) create mode 100644 doc/guides/howto/virtio_paths_selection_and_usage.rst diff --git a/doc/guides/howto/index.rst b/doc/guides/howto/index.rst index a4c131652..6edb8d5be 100644 --- a/doc/guides/howto/index.rst +++ b/doc/guides/howto/index.rst @@ -16,6 +16,7 @@ HowTo Guides vfd virtio_user_for_container_networking virtio_user_as_exceptional_path + virtio_paths_selection_and_usage packet_capture_framework telemetry debug_troubleshoot 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..9bf7f8ef7 --- /dev/null +++ b/doc/guides/howto/virtio_paths_selection_and_usage.rst @@ -0,0 +1,126 @@ +.. 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 combination of virtio features +(Rx mergeable, In-order, Packed virtqueue), below is an introduction of these +features: + +* `Rx mergeable `_: With this feature negotiated, device + can receive large 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. With this feature negotiated, + driver will use descriptors in order. +* `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 make it easier + for hardware to implement. + +Virtio paths Selection +---------------------- + +If packed virtqueue is not negotiated, below split virtqueue paths will 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 will be selected. +#. Split virtqueue in-order mergeable path: If Rx mergeable and in-order feature are + both negotiated, this path will be selected. +#. Split virtqueue in-order non-mergeable path: If in-order feature is negotiated and + Rx mergeable is not negotiated, this path will be selected. +#. Split virtqueue vectorized Rx path: If Rx mergeable is disabled and no Rx offload + requested, this path will be selected. + +If packed virtqueue is negotiated, below packed virtqueue paths will 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, this path will be selected. +#. Packed virtqueue in-order mergeable path: If in-order and Rx mergeable feature 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 description, virtio path and corresponding Rx/Tx callbacks will +be selected automatically. Rx callbacks and Tx callbacks for each virtio path +are shown in below table: + +.. table:: Virtio Paths and Callbacks + + ============================================ ================================= ======================== + Virtio paths 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 non-meregable 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 non-mergeable path virtio_recv_pkts_packed virtio_xmit_pkts_packed + ============================================ ================================= ======================== + +Virtio paths Support Status from Release to Release +--------------------------------------------------- + +Virtio feature implementation: + +* In-order feature is supported since DPDK 18.08 by adding new Rx/Tx callbacks + ``virtio_recv_pkts_inorder`` and ``virtio_xmit_pkts_inorder``. +* Packed virtqueue is supported since DPDK 19.02 by adding new Rx/Tx callbacks + ``virtio_recv_pkts_packed`` , ``virtio_recv_mergeable_pkts_packed`` and + ``virtio_xmit_pkts_packed``. + +All virtio paths support status are shown in below table: + +.. table:: Virtio Paths and Releases + + ============================================ ============= ============= ============= + Virtio paths 16.11 ~ 18.05 18.08 ~ 18.11 19.02 ~ 19.11 + ============================================ ============= ============= ============= + Split virtqueue mergeable path Y Y Y + Split virtqueue non-mergeable path Y Y Y + Split virtqueue vectorized Rx path Y Y Y + Split virtqueue simple Tx path Y N N + Split virtqueue in-order mergeable path Y Y + Split virtqueue in-order non-mergeable path Y Y + Packed virtqueue mergeable path Y + Packed virtqueue non-mergeable path Y + Packed virtqueue in-order mergeable path Y + Packed virtqueue in-order non-mergeable path Y + ============================================ ============= ============= ============= + +QEMU Support Status +------------------- + +* Qemu now supports three paths of split virtqueue: Split virtqueue mergeable path, + Split virtqueue non-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