doc: clarify virtio PMD path selection
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Commit Message
From: Yinan Wang <yinan.wang@intel.com>
add virtio paths selection and usage introduction for better
virtio usability.
Signed-off-by: Yinan Wang <yinan.wang@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
Comments
On Mon, 18 Nov 2019 05:29:23 -0500
Yinan <yinan.wang@intel.com> wrote:
> From: Yinan Wang <yinan.wang@intel.com>
>
> add virtio paths selection and usage introduction for better
> virtio usability.
>
> Signed-off-by: Yinan Wang <yinan.wang@intel.com>
> ---
Nice to have this documented.
Do you think it would make sense to link to the virtio standard that defines this?
Hi Yinan,
> -----Original Message-----
> From: dev <dev-bounces@dpdk.org> On Behalf Of Yinan
> Sent: Monday, November 18, 2019 6:29 PM
> 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 <yinan.wang@intel.com>
> Subject: [dpdk-dev] [PATCH] doc: clarify virtio PMD path selection
>
> From: Yinan Wang <yinan.wang@intel.com>
>
> add virtio paths selection and usage introduction for better
> virtio usability.
>
> Signed-off-by: Yinan Wang <yinan.wang@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.hu@arm.com>
Thanks your suggestion, I will add the link in v2 version.
> -----Original Message-----
> From: Stephen Hemminger <stephen@networkplumber.org>
> Sent: 2019年11月18日 10:24
> To: Wang, Yinan <yinan.wang@intel.com>
> Cc: dev@dpdk.org; maxime.coquelin@redhat.com; Bie, Tiwei
> <tiwei.bie@intel.com>; Wang, Zhihong <zhihong.wang@intel.com>;
> Mcnamara, John <john.mcnamara@intel.com>; Kovacevic, Marko
> <marko.kovacevic@intel.com>
> Subject: Re: [dpdk-dev] [PATCH] doc: clarify virtio PMD path selection
>
> On Mon, 18 Nov 2019 05:29:23 -0500
> Yinan <yinan.wang@intel.com> wrote:
>
> > From: Yinan Wang <yinan.wang@intel.com>
> >
> > add virtio paths selection and usage introduction for better virtio
> > usability.
> >
> > Signed-off-by: Yinan Wang <yinan.wang@intel.com>
> > ---
>
>
> Nice to have this documented.
> Do you think it would make sense to link to the virtio standard that defines this?
18/11/2019 11:29, Yinan:
+--------------------------------------------------------------------------------------------------------------------------------------------------------+
> + |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 |
> + ---------------------------------------------------------------------------------------------------------------------------------------------------------+
Please try to make the table shorter.
I think there would be some gain to name versions without "v"
and use a simple table syntax:
http://docutils.sourceforge.net/docs/user/rst/quickref.html#tables
new file mode 100644
@@ -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.