| Message ID | 20190625145724.3058-3-ktraynor@redhat.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | vhost tx retry updates | expand |
Bleep bloop. Greetings Kevin Traynor, I am a robot and I have tried out your patch.
Thanks for your contribution.
I encountered some error that I wasn't expecting. See the details below.
checkpatch:
WARNING: Line is 81 characters long (recommended limit is 79)
#48 FILE: Documentation/topics/dpdk/vhost-user.rst:103:
<address type='pci' domain='0x0000' bus='0x00' slot='0x10' function='0x0'/>
Lines checked: 64, Warnings: 1, Errors: 0
Please check this out. If you feel there has been an error, please email aconole@bytheb.org
Thanks,
0-day Robot
On Tue, Jun 25, 2019 at 03:57:22PM +0100, Kevin Traynor wrote: > Add documentation about vhost tx retries and external > configuration that can help reduce/avoid them. > > Signed-off-by: Kevin Traynor <ktraynor@redhat.com> > Acked-by: Eelco Chaudron <echaudro@redhat.com> > --- This also has a magic number without a define, but since the max number of retries is exposed to the users in the next patches as a parameter in the documentation it seems fine to me. Otherwise the patch looks good to me. Acked-by: Flavio Leitner <fbl@sysclose.org>
On Wed, Jun 26, 2019 at 11:05:42AM -0300, Flavio Leitner via dev wrote: > On Tue, Jun 25, 2019 at 03:57:22PM +0100, Kevin Traynor wrote: > > Add documentation about vhost tx retries and external > > configuration that can help reduce/avoid them. > > > > Signed-off-by: Kevin Traynor <ktraynor@redhat.com> > > Acked-by: Eelco Chaudron <echaudro@redhat.com> > > --- > > This also has a magic number without a define, but since the > max number of retries is exposed to the users in the next patches > as a parameter in the documentation it seems fine to me. > > Otherwise the patch looks good to me. Actually it mentions NETDEV_MAX_BATCH where it is NETDEV_MAX_BURST as defined in lib/dp-packet.h fbl
On 26/06/2019 15:27, Flavio Leitner wrote: > On Wed, Jun 26, 2019 at 11:05:42AM -0300, Flavio Leitner via dev wrote: >> On Tue, Jun 25, 2019 at 03:57:22PM +0100, Kevin Traynor wrote: >>> Add documentation about vhost tx retries and external >>> configuration that can help reduce/avoid them. >>> >>> Signed-off-by: Kevin Traynor <ktraynor@redhat.com> >>> Acked-by: Eelco Chaudron <echaudro@redhat.com> >>> --- >> >> This also has a magic number without a define, but since the >> max number of retries is exposed to the users in the next patches >> as a parameter in the documentation it seems fine to me. >> >> Otherwise the patch looks good to me. > > Actually it mentions NETDEV_MAX_BATCH where it is NETDEV_MAX_BURST > as defined in lib/dp-packet.h > D'oh :/ thanks for spotting it. > fbl >
diff --git a/Documentation/topics/dpdk/vhost-user.rst b/Documentation/topics/dpdk/vhost-user.rst index f7b4b338e..0f426c14c 100644 --- a/Documentation/topics/dpdk/vhost-user.rst +++ b/Documentation/topics/dpdk/vhost-user.rst @@ -76,4 +76,40 @@ mode ports require QEMU version 2.7. Ports of type vhost-user are currently deprecated and will be removed in a future release. +vhost tx retries +~~~~~~~~~~~~~~~~ + +When sending a batch of packets to a vhost-user or vhost-user-client interface, +it may happen that some but not all of the packets in the batch are able to be +sent to the guest. This is often because there is not enough free descriptors +in the virtqueue for all the packets in the batch to be sent. In this case +there will be a retry, with a default maximum of 8 occurring. If at any time no +packets can be sent, it may mean the guest is not accepting packets, so there +are no (more) retries. + +.. note:: + + Maximum vhost tx batch size is defined by NETDEV_MAX_BATCH and is + currently 32. + +Tx Retries may be reduced or even avoided by some external configuration, such +as increasing the virtqueue size through the ``rx_queue_size`` parameter +introduced in QEMU 2.7.0 / libvirt 2.3.0:: + + <interface type='vhostuser'> + <mac address='56:48:4f:53:54:01'/> + <source type='unix' path='/tmp/dpdkvhostclient0' mode='server'/> + <model type='virtio'/> + <driver name='vhost' rx_queue_size='1024' tx_queue_size='1024'/> + <address type='pci' domain='0x0000' bus='0x00' slot='0x10' function='0x0'/> + </interface> + +The guest application will also need need to provide enough descriptors. For +example with ``testpmd`` the command line argument can be used:: + + --rxd=1024 --txd=1024 + +The guest should also have sufficient cores dedicated for consuming and +processing packets at the required rate. + .. _dpdk-vhost-user: