On Tue, 2021-09-28 at 15:05 +0530, Jerin Jacob wrote:

On Sun, Sep 26, 2021 at 11:06 AM Xueming(Steven) Li [off-list ref] wrote:

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On Wed, 2021-08-11 at 13:04 +0100, Ferruh Yigit wrote:

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On 8/11/2021 9:28 AM, Xueming(Steven) Li wrote:

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-----Original Message-----
From: Jerin Jacob <redacted>
Sent: Wednesday, August 11, 2021 4:03 PM
To: Xueming(Steven) Li <redacted>
Cc: dpdk-dev <redacted>; Ferruh Yigit <redacted>; NBU-Contact-Thomas Monjalon <redacted>;
Andrew Rybchenko [off-list ref]
Subject: Re: [dpdk-dev] [PATCH v1] ethdev: introduce shared Rx queue

On Mon, Aug 9, 2021 at 7:46 PM Xueming(Steven) Li [off-list ref] wrote:

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Hi,

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-----Original Message-----
From: Jerin Jacob <redacted>
Sent: Monday, August 9, 2021 9:51 PM
To: Xueming(Steven) Li <redacted>
Cc: dpdk-dev <redacted>; Ferruh Yigit <redacted>;
NBU-Contact-Thomas Monjalon [off-list ref]; Andrew Rybchenko
[off-list ref]
Subject: Re: [dpdk-dev] [PATCH v1] ethdev: introduce shared Rx queue

On Mon, Aug 9, 2021 at 5:18 PM Xueming Li [off-list ref] wrote:

quoted

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 is supposed to be polled on same thread.

Multiple groups is supported by group ID.

Is this offload specific to the representor? If so can this name be changed specifically to representor?

Yes, PF and representor in switch domain could take advantage.

quoted

If it is for a generic case, how the flow ordering will be maintained?

Not quite sure that I understood your question. The control path of is
almost same as before, PF and representor port still needed, rte flows not impacted.
Queues still needed for each member port, descriptors(mbuf) will be
supplied from shared Rx queue in my PMD implementation.

My question was if create a generic RTE_ETH_RX_OFFLOAD_SHARED_RXQ offload, multiple ethdev receive queues land into the same
receive queue, In that case, how the flow order is maintained for respective receive queues.

I guess the question is testpmd forward stream? The forwarding logic has to be changed slightly in case of shared rxq.
basically for each packet in rx_burst result, lookup source stream according to mbuf->port, forwarding to target fs.
Packets from same source port could be grouped as a small burst to process, this will accelerates the performance if traffic come from
limited ports. I'll introduce some common api to do shard rxq forwarding, call it with packets handling callback, so it suites for
all forwarding engine. Will sent patches soon.

All ports will put the packets in to the same queue (share queue), right? Does
this means only single core will poll only, what will happen if there are
multiple cores polling, won't it cause problem?

And if this requires specific changes in the application, I am not sure about
the solution, can't this work in a transparent way to the application?

Discussed with Jerin, new API introduced in v3 2/8 that aggregate ports
in same group into one new port. Users could schedule polling on the
aggregated port instead of all member ports.

The v3 still has testpmd changes in fastpath. Right? IMO, For this
feature, we should not change fastpath of testpmd
application. Instead, testpmd can use aggregated ports probably as
separate fwd_engine to show how to use this feature.

Good point to discuss :) There are two strategies to polling a shared
Rxq:
1. polling each member port
   All forwarding engines can be reused to work as before. 
   My testpmd patches are efforts towards this direction.
   Does your PMD support this?
2. polling aggregated port
   Besides forwarding engine, need more work to to demo it.
   This is an optional API, not supported by my PMD yet.

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Overall, is this for optimizing memory for the port represontors? If so can't we
have a port representor specific solution, reducing scope can reduce the
complexity it brings?

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If this offload is only useful for representor case, Can we make this offload specific to representor the case by changing its name and
scope.

It works for both PF and representors in same switch domain, for application like OVS, few changes to apply.

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Signed-off-by: Xueming Li <redacted>
---
 doc/guides/nics/features.rst                    | 11 +++++++++++
 doc/guides/nics/features/default.ini            |  1 +
 doc/guides/prog_guide/switch_representation.rst | 10 ++++++++++
 lib/ethdev/rte_ethdev.c                         |  1 +
 lib/ethdev/rte_ethdev.h                         |  7 +++++++
 5 files changed, 30 insertions(+)

diff --git a/doc/guides/nics/features.rst

b/doc/guides/nics/features.rst index a96e12d155..2e2a9b1554 100644

--- a/doc/guides/nics/features.rst
+++ b/doc/guides/nics/features.rst

@@ -624,6 +624,17 @@ Supports inner packet L4 checksum.
   ``tx_offload_capa,tx_queue_offload_capa:DEV_TX_OFFLOAD_OUTER_UDP_CKSUM``.


+.. _nic_features_shared_rx_queue:
+
+Shared Rx queue
+---------------
+
+Supports shared Rx queue for ports in same switch domain.
+
+* **[uses]     rte_eth_rxconf,rte_eth_rxmode**: ``offloads:RTE_ETH_RX_OFFLOAD_SHARED_RXQ``.
+* **[provides] mbuf**: ``mbuf.port``.
+
+
 .. _nic_features_packet_type_parsing:

 Packet type parsing

diff --git a/doc/guides/nics/features/default.ini

b/doc/guides/nics/features/default.ini
index 754184ddd4..ebeb4c1851 100644

--- a/doc/guides/nics/features/default.ini
+++ b/doc/guides/nics/features/default.ini

@@ -19,6 +19,7 @@ Free Tx mbuf on demand =
 Queue start/stop     =
 Runtime Rx queue setup =
 Runtime Tx queue setup =
+Shared Rx queue      =
 Burst mode info      =
 Power mgmt address monitor =
 MTU update           =

diff --git a/doc/guides/prog_guide/switch_representation.rst

b/doc/guides/prog_guide/switch_representation.rst
index ff6aa91c80..45bf5a3a10 100644

--- a/doc/guides/prog_guide/switch_representation.rst
+++ b/doc/guides/prog_guide/switch_representation.rst

@@ -123,6 +123,16 @@ thought as a software "patch panel" front-end for applications.
 .. [1] `Ethernet switch device driver model (switchdev)

<https://www.kernel.org/doc/Documentation/networking/switchdev.txt

quoted

`_

+- Memory usage of representors is huge when number of representor
+grows,
+  because PMD always allocate mbuf for each descriptor of Rx queue.
+  Polling the large number of ports brings more CPU load, cache
+miss and
+  latency. Shared Rx queue can be used to share Rx queue between
+PF and
+  representors in same switch domain.
+``RTE_ETH_RX_OFFLOAD_SHARED_RXQ``
+  is present in Rx offloading capability of device info. Setting
+the
+  offloading flag in device Rx mode or Rx queue configuration to
+enable
+  shared Rx queue. Polling any member port of shared Rx queue can
+return
+  packets of all ports in group, port ID is saved in ``mbuf.port``.
+
 Basic SR-IOV
 ------------

diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
index 9d95cd11e1..1361ff759a 100644
--- a/lib/ethdev/rte_ethdev.c
+++ b/lib/ethdev/rte_ethdev.c

@@ -127,6 +127,7 @@ static const struct {
        RTE_RX_OFFLOAD_BIT2STR(OUTER_UDP_CKSUM),
        RTE_RX_OFFLOAD_BIT2STR(RSS_HASH),
        RTE_ETH_RX_OFFLOAD_BIT2STR(BUFFER_SPLIT),
+       RTE_ETH_RX_OFFLOAD_BIT2STR(SHARED_RXQ),
 };

 #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. */
        /**
         * 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