[dpdk-dev,v3] doc: virtio PMD Rx/Tx callbacks
Commit Message
This patch explains current virtio PMD Rx/Tx callbacks, to help understand
what's the difference, and how to enable the right ones.
Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
Acked-by: John McNamara <john.mcnamara@intel.com>
--------------
Changes in v3:
1. Rephrase for clearer description.
--------------
Changes in v2:
1. Changes on format and few descriptions.
---
doc/guides/nics/virtio.rst | 75 ++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 69 insertions(+), 6 deletions(-)
Comments
On Thu, Jun 30, 2016 at 11:28:01PM -0400, Zhihong Wang wrote:
> This patch explains current virtio PMD Rx/Tx callbacks, to help understand
> what's the difference, and how to enable the right ones.
>
> Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
> Acked-by: John McNamara <john.mcnamara@intel.com>
Applied to dpdk-next-virtio.
> --------------
> Changes in v3:
However, this is still wrong. It must start with 3 dashes, ---.
$ man git am
The patch is expected to be inline, directly following the
message. Any line that is of the form:
· three-dashes and end-of-line, or
· a line that begins with "diff -", or
· a line that begins with "Index: "
is taken as the beginning of a patch, and the commit log message
is terminated before the first occurrence of such a line.
This is just a note; I have fixed it while apply.
--yliu
> -----Original Message-----
> From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com]
> Sent: Monday, July 4, 2016 10:57 AM
> To: Wang, Zhihong <zhihong.wang@intel.com>
> Cc: dev@dpdk.org; Richardson, Bruce <bruce.richardson@intel.com>; Mcnamara,
> John <john.mcnamara@intel.com>
> Subject: Re: [PATCH v3] doc: virtio PMD Rx/Tx callbacks
>
> On Thu, Jun 30, 2016 at 11:28:01PM -0400, Zhihong Wang wrote:
> > This patch explains current virtio PMD Rx/Tx callbacks, to help understand
> > what's the difference, and how to enable the right ones.
> >
> > Signed-off-by: Zhihong Wang <zhihong.wang@intel.com>
> > Acked-by: John McNamara <john.mcnamara@intel.com>
>
> Applied to dpdk-next-virtio.
>
> > --------------
> > Changes in v3:
>
> However, this is still wrong. It must start with 3 dashes, ---.
>
> $ man git am
>
> The patch is expected to be inline, directly following the
> message. Any line that is of the form:
>
> * three-dashes and end-of-line, or
>
> * a line that begins with "diff -", or
>
> * a line that begins with "Index: "
>
> is taken as the beginning of a patch, and the commit log message
> is terminated before the first occurrence of such a line.
>
>
> This is just a note; I have fixed it while apply.
Noted. Thanks!
>
> --yliu
@@ -73,7 +73,7 @@ In this release, the virtio PMD driver provides the basic functionality of packe
* It supports multicast packets and promiscuous mode.
-* The descriptor number for the RX/TX queue is hard-coded to be 256 by qemu.
+* The descriptor number for the Rx/Tx queue is hard-coded to be 256 by qemu.
If given a different descriptor number by the upper application,
the virtio PMD generates a warning and fall back to the hard-coded value.
@@ -163,8 +163,9 @@ Host2VM communication example
which means received packets come from vEth0, and transmitted packets is sent to vEth0.
#. In the guest, bind the virtio device to the uio_pci_generic kernel module and start the forwarding application.
- When the virtio port in guest bursts rx, it is getting packets from the raw socket's receive queue.
- When the virtio port bursts tx, it is sending packet to the tx_q.
+ When the virtio port in guest bursts Rx, it is getting packets from the
+ raw socket's receive queue.
+ When the virtio port bursts Tx, it is sending packet to the tx_q.
.. code-block:: console
@@ -183,7 +184,9 @@ Host2VM communication example
The packet reception and transmission flow path is:
- IXIA packet generator->82599 PF->KNI rx queue->KNI raw socket queue->Guest VM virtio port 0 rx burst->Guest VM virtio port 0 tx burst-> KNI tx queue->82599 PF-> IXIA packet generator
+ IXIA packet generator->82599 PF->KNI Rx queue->KNI raw socket queue->Guest
+ VM virtio port 0 Rx burst->Guest VM virtio port 0 Tx burst-> KNI Tx queue
+ ->82599 PF-> IXIA packet generator
Virtio with qemu virtio Back End
--------------------------------
@@ -206,8 +209,68 @@ Virtio with qemu virtio Back End
In this example, the packet reception flow path is:
- IXIA packet generator->82599 PF->Linux Bridge->TAP0's socket queue-> Guest VM virtio port 0 rx burst-> Guest VM 82599 VF port1 tx burst-> IXIA packet generator
+ IXIA packet generator->82599 PF->Linux Bridge->TAP0's socket queue-> Guest
+ VM virtio port 0 Rx burst-> Guest VM 82599 VF port1 Tx burst-> IXIA packet
+ generator
The packet transmission flow is:
- IXIA packet generator-> Guest VM 82599 VF port1 rx burst-> Guest VM virtio port 0 tx burst-> tap -> Linux Bridge->82599 PF-> IXIA packet generator
+ IXIA packet generator-> Guest VM 82599 VF port1 Rx burst-> Guest VM virtio
+ port 0 Tx burst-> tap -> Linux Bridge->82599 PF-> IXIA packet generator
+
+
+Virtio PMD Rx/Tx Callbacks
+--------------------------
+
+Virtio driver has 3 Rx callbacks and 2 Tx callbacks.
+
+Rx callbacks:
+
+#. ``virtio_recv_pkts``:
+ Regular version without mergeable Rx buffer support.
+
+#. ``virtio_recv_mergeable_pkts``:
+ Regular version with mergeable Rx buffer support.
+
+#. ``virtio_recv_pkts_vec``:
+ Vector version without mergeable Rx buffer support, also fixes the available
+ ring indexes and uses vector instructions to optimize performance.
+
+Tx callbacks:
+
+#. ``virtio_xmit_pkts``:
+ Regular version.
+
+#. ``virtio_xmit_pkts_simple``:
+ Vector version fixes the available ring indexes to optimize performance.
+
+
+By default, the non-vector callbacks are used:
+
+* For Rx: If mergeable Rx buffers is disabled then ``virtio_recv_pkts`` is
+ used; otherwise ``virtio_recv_mergeable_pkts``.
+
+* For Tx: ``virtio_xmit_pkts``.
+
+
+Vector callbacks will be used when:
+
+* ``txq_flags`` is set to ``VIRTIO_SIMPLE_FLAGS`` (0xF01), which implies:
+
+ * Single segment is specified.
+
+ * No offload support is needed.
+
+* Mergeable Rx buffers is disabled.
+
+The corresponding callbacks are:
+
+* For Rx: ``virtio_recv_pkts_vec``.
+
+* For Tx: ``virtio_xmit_pkts_simple``.
+
+
+Example of using the vector version of the virtio poll mode driver in
+``testpmd``::
+
+ testpmd -c 0x7 -n 4 -- -i --txqflags=0xF01 --rxq=1 --txq=1 --nb-cores=1