[dpdk-dev] [PATCH v2 01/15] ethdev: introduce shared Rx queue

[Jerin Jacob]

On Wed, Aug 18, 2021 at 4:44 PM Xueming(Steven) Li <xuemingl at nvidia.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Jerin Jacob <jerinjacobk at gmail.com>
> > Sent: Tuesday, August 17, 2021 11:12 PM
> > To: Xueming(Steven) Li <xuemingl at nvidia.com>
> > Cc: dpdk-dev <dev at dpdk.org>; Ferruh Yigit <ferruh.yigit at intel.com>; NBU-Contact-Thomas Monjalon <thomas at monjalon.net>;
> > Andrew Rybchenko <andrew.rybchenko at oktetlabs.ru>
> > Subject: Re: [PATCH v2 01/15] ethdev: introduce shared Rx queue
> >
> > On Tue, Aug 17, 2021 at 5:01 PM Xueming(Steven) Li <xuemingl at nvidia.com> wrote:
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Jerin Jacob <jerinjacobk at gmail.com>
> > > > Sent: Tuesday, August 17, 2021 5:33 PM
> > > > To: Xueming(Steven) Li <xuemingl at nvidia.com>
> > > > Cc: dpdk-dev <dev at dpdk.org>; Ferruh Yigit <ferruh.yigit at intel.com>;
> > > > NBU-Contact-Thomas Monjalon <thomas at monjalon.net>; Andrew Rybchenko
> > > > <andrew.rybchenko at oktetlabs.ru>
> > > > Subject: Re: [PATCH v2 01/15] ethdev: introduce shared Rx queue
> > > >
> > > > On Wed, Aug 11, 2021 at 7:34 PM Xueming Li <xuemingl at nvidia.com> wrote:
> > > > >
> > > > > In current DPDK framework, each RX queue is pre-loaded with mbufs
> > > > > for incoming packets. When number of representors scale out in a
> > > > > switch domain, the memory consumption became significant. Most
> > > > > important, polling all ports leads to high cache miss, high
> > > > > latency and low throughput.
> > > > >
> > > > > This patch introduces shared RX queue. Ports with same
> > > > > configuration in a switch domain could share RX queue set by specifying sharing group.
> > > > > Polling any queue using same shared RX queue receives packets from
> > > > > all member ports. Source port is identified by mbuf->port.
> > > > >
> > > > > Port queue number in a shared group should be identical. Queue
> > > > > index is
> > > > > 1:1 mapped in shared group.
> > > > >
> > > > > Share RX queue must be polled on single thread or core.
> > > > >
> > > > > Multiple groups is supported by group ID.
> > > > >
> > > > > Signed-off-by: Xueming Li <xuemingl at nvidia.com>
> > > > > Cc: Jerin Jacob <jerinjacobk at gmail.com>
> > > > > ---
> > > > > Rx queue object could be used as shared Rx queue object, it's
> > > > > important to clear all queue control callback api that using queue object:
> > > > >   https://mails.dpdk.org/archives/dev/2021-July/215574.html
> > > >
> > > > >  #undef RTE_RX_OFFLOAD_BIT2STR
> > > > > diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h
> > > > > index d2b27c351f..a578c9db9d 100644
> > > > > --- a/lib/ethdev/rte_ethdev.h
> > > > > +++ b/lib/ethdev/rte_ethdev.h
> > > > > @@ -1047,6 +1047,7 @@ struct rte_eth_rxconf {
> > > > >         uint8_t rx_drop_en; /**< Drop packets if no descriptors are available. */
> > > > >         uint8_t rx_deferred_start; /**< Do not start queue with rte_eth_dev_start(). */
> > > > >         uint16_t rx_nseg; /**< Number of descriptions in rx_seg array.
> > > > > */
> > > > > +       uint32_t shared_group; /**< Shared port group index in
> > > > > + switch domain. */
> > > >
> > > > Not to able to see anyone setting/creating this group ID test application.
> > > > How this group is created?
> > >
> > > Nice catch, the initial testpmd version only support one default group(0).
> > > All ports that supports shared-rxq assigned in same group.
> > >
> > > We should be able to change "--rxq-shared" to "--rxq-shared-group" to
> > > support group other than default.
> > >
> > > To support more groups simultaneously, need to consider testpmd
> > > forwarding stream core assignment, all streams in same group need to stay on same core.
> > > It's possible to specify how many ports to increase group number, but
> > > user must schedule stream affinity carefully - error prone.
> > >
> > > On the other hand, one group should be sufficient for most customer,
> > > the doubt is whether it valuable to support multiple groups test.
> >
> > Ack. One group is enough in testpmd.
> >
> > My question was more about who and how this group is created, Should n't we need API to create shared_group? If we do the
> > following, at least, I can think, how it can be implemented in SW or other HW.
> >
> > - Create aggregation queue group
> > - Attach multiple  Rx queues to the aggregation queue group
> > - Pull the packets from the queue group(which internally fetch from the Rx queues _attached_)
> >
> > Does the above kind of sequence, break your representor use case?
>
> Seems more like a set of EAL wrapper. Current API tries to minimize the application efforts to adapt shared-rxq.
> - step 1, not sure how important it is to create group with API, in rte_flow, group is created on demand.

Which rte_flow pattern/action for this?

> - step 2, currently, the attaching is done in rte_eth_rx_queue_setup, specify offload and group in rx_conf struct.
> - step 3, define a dedicate api to receive packets from shared rxq? Looks clear to receive packets from shared rxq.
>   currently, rxq objects in share group is same - the shared rxq, so the eth callback eth_rx_burst_t(rxq_obj, mbufs, n) could
>   be used to receive packets from any ports in group, normally the first port(PF) in group.
>   An alternative way is defining a vdev with same queue number and copy rxq objects will make the vdev a proxy of
>   the shared rxq group - this could be an helper API.
>
> Anyway the wrapper doesn't break use case, step 3 api is more clear, need to understand how to implement efficiently.

Are you doing this feature based on any HW support or it just pure SW
thing, If it is SW, It is better to have
just new vdev for like drivers/net/bonding/. This we can help
aggregate multiple Rxq across the multiple ports
of same the driver.


>
> >
> >
> > >
> > > >
> > > >
> > > > >         /**
> > > > >          * Per-queue Rx offloads to be set using DEV_RX_OFFLOAD_* flags.
> > > > >          * Only offloads set on rx_queue_offload_capa or
> > > > > rx_offload_capa @@ -1373,6 +1374,12 @@ struct rte_eth_conf {
> > > > > #define DEV_RX_OFFLOAD_OUTER_UDP_CKSUM  0x00040000
> > > > >  #define DEV_RX_OFFLOAD_RSS_HASH                0x00080000
> > > > >  #define RTE_ETH_RX_OFFLOAD_BUFFER_SPLIT 0x00100000
> > > > > +/**
> > > > > + * Rx queue is shared among ports in same switch domain to save
> > > > > +memory,
> > > > > + * avoid polling each port. Any port in group can be used to receive packets.
> > > > > + * Real source port number saved in mbuf->port field.
> > > > > + */
> > > > > +#define RTE_ETH_RX_OFFLOAD_SHARED_RXQ   0x00200000
> > > > >
> > > > >  #define DEV_RX_OFFLOAD_CHECKSUM (DEV_RX_OFFLOAD_IPV4_CKSUM | \
> > > > >                                  DEV_RX_OFFLOAD_UDP_CKSUM | \
> > > > > --
> > > > > 2.25.1
> > > > >