Hi Yinan, > -----Original Message----- > From: dev <dev-boun...@dpdk.org> On Behalf Of Yinan > Sent: Monday, November 18, 2019 6:29 PM > To: dev@dpdk.org; maxime.coque...@redhat.com; tiwei....@intel.com > Cc: zhihong.w...@intel.com; john.mcnam...@intel.com; > marko.kovace...@intel.com; Yinan Wang <yinan.w...@intel.com> > Subject: [dpdk-dev] [PATCH] doc: clarify virtio PMD path selection > > From: Yinan Wang <yinan.w...@intel.com> > > add virtio paths selection and usage introduction for better > virtio usability. > > Signed-off-by: Yinan Wang <yinan.w...@intel.com> > --- > .../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: s/are/is an > + > +* 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 > +------------------- It is better to add Qemu version latest, the future Qemu version may support more. > + > +Qemu only support three path of Virtio-PMD: Split virtqueue mergebale path, Add "s" to the first 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
Other than the minor comments, Reviewed-by: Gavin Hu <gavin...@arm.com>
