Re: [ovs-dev] [PATCH RESEND v11] netdev-dpdk: Add custom rx-steering configuration.
Kevin Traynor, Jun 15, 2023 at 12:53:
> > new_n_rxq = MAX(smap_get_int(args, "n_rxq", NR_QUEUE), 1);
> > +if (dev->requested_rx_steer_flags != 0) {
> > +new_n_rxq += 1;
>
> If rx-steering is set for the port and the flow has previously not been
> able to be offloaded, the dev->requested_n_rxq will always be different
> than the netdev->n_rxq. That means this device will do a reconfigure
> anytime there is a config change on any device.
>
> e.g. If rx sterring on device A and device A cannot offload flows (this
> is acceptable). Any config change to device B will result in reconfigure
> of device A, not based on flags but based on num of rxqs.
This is why I had added an intermediate dev->user_n_rxq field in v10.
I tried to get rid of it as you suggested but it causes this issue.
Also, I think there's another side effect that is actually worse, if the
rte flow offload fails, dev->requested_n_rxq is decremented by one. If
netdev_dpdk_reconfigure() is called without reinitializing
dev->requested_n_rxq (mtu change or some other event), the value will
eventually drop down to zero and then to negative values.
I'll reintroduce user_n_rxq as an intermediate value that cannot be
modified other by than the user so that these problems cannot occur.
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Re: [ovs-dev] [PATCH RESEND v11] netdev-dpdk: Add custom rx-steering configuration.
On 01/06/2023 10:29, Robin Jarry wrote: Some control protocols are used to maintain link status between forwarding engines (e.g. LACP). When the system is not sized properly, the PMD threads may not be able to process all incoming traffic from the configured Rx queues. When a signaling packet of such protocols is dropped, it can cause link flapping, worsening the situation. Use the RTE flow API to redirect these protocols into a dedicated Rx queue. The assumption is made that the ratio between control protocol traffic and user data traffic is very low and thus this dedicated Rx queue will never get full. Re-program the RSS redirection table to only use the other Rx queues. The additional Rx queue will be assigned a PMD core like any other Rx queue. Polling that extra queue may introduce increased latency and a slight performance penalty at the benefit of preventing link flapping. This feature must be enabled per port on specific protocols via the rx-steering option. This option takes "rss" followed by a "+" separated list of protocol names. It is only supported on ethernet ports. This feature is experimental. If the user has already configured multiple Rx queues on the port, an additional one will be allocated for packets. If the hardware cannot satisfy the requested number of requested Rx queues, the last Rx queue will be assigned for control plane. If only one Rx queue is available, the rx-steering feature will be disabled. If the hardware does not support the RTE flow matchers/actions, the feature will be disabled. It cannot be enabled when other_config:hw-offload=true as it may conflict with the offloaded RTE flows. Similarly, if hw-offload is enabled, custom rx-steering will be forcibly disabled on all ports. Example use: ovs-vsctl add-bond br-phy bond0 phy0 phy1 -- \ set interface phy0 type=dpdk options:dpdk-devargs=:ca:00.0 -- \ set interface phy0 options:rx-steering=rss+lacp -- \ set interface phy1 type=dpdk options:dpdk-devargs=:ca:00.1 -- \ set interface phy1 options:rx-steering=rss+lacp As a starting point, only one protocol is supported: LACP. Other protocols can be added in the future. NIC compatibility should be checked. To validate that this works as intended, I used a traffic generator to generate random traffic slightly above the machine capacity at line rate on a two ports bond interface. OVS is configured to receive traffic on two VLANs and pop/push them in a br-int bridge based on tags set on patch ports. +--+ | DUT | |++| || br-int || in_port=patch10,actions=mod_dl_src:$patch11,mod_dl_dst:$tgen1,output:patch11 |||| in_port=patch11,actions=mod_dl_src:$patch10,mod_dl_dst:$tgen0,output:patch10 || patch10patch11 || |+---|---|+| || | | |+---|---|+| || patch00patch01 || || tag:10tag:20 || |||| || br-phy || default flow, action=NORMAL |||| || bond0|| balance-slb, lacp=passive, lacp-time=fast ||phy0 phy1 || |+--|-|---+| +---|-|+ | | +---|-|+ | port0 port1 | balance L3/L4, lacp=active, lacp-time=fast | lag | mode trunk VLANs 10, 20 | | |switch| | | | vlan 10vlan 20 | mode access | port2 port3 | +-|--|-+ | | +-|--|-+ | tgen0 tgen1 | Random traffic that is properly balanced | | across the bond ports in both directions. | traffic generator | +--+ Without rx-steering, the bond0 links are randomly switching to "defaulted" when one of the LACP packets sent by the switch is dropped because the RX queues are full and the PMD threads did not process them fast enough. When that happens, all traffic must go through a single link which causes above line rate traffic to be dropped. ~# ovs-appctl lacp/show-stats bond0 bond0 statistics member: phy0: TX PDUs: 347246 RX PDUs: 14865 RX Bad PDUs: 0 RX Marker Request PDUs: 0 Link Expired: 168 Link Defaulted: 0 Carrier Status Changed: 0 member: phy1: TX PDUs: 347245 RX PDUs: 14919 RX Bad PDUs: 0 RX Marker Request PDUs: 0 Link Expired: 147 Link Defaulted: 1 Carrier Status Changed: 0 When rx-steering is enabled, no LACP packet is dropped and the bond links remain enabled at all times, maximizing the throughput. Neither the "Link Expired" nor the "Link Defaulted" counters are incremented anymore. This feature may be considered as "QoS". However, it does not work by limiting the rate of traffic explicitly. It only guarantees that some protocols
[ovs-dev] [PATCH RESEND v11] netdev-dpdk: Add custom rx-steering configuration.
Some control protocols are used to maintain link status between forwarding engines (e.g. LACP). When the system is not sized properly, the PMD threads may not be able to process all incoming traffic from the configured Rx queues. When a signaling packet of such protocols is dropped, it can cause link flapping, worsening the situation. Use the RTE flow API to redirect these protocols into a dedicated Rx queue. The assumption is made that the ratio between control protocol traffic and user data traffic is very low and thus this dedicated Rx queue will never get full. Re-program the RSS redirection table to only use the other Rx queues. The additional Rx queue will be assigned a PMD core like any other Rx queue. Polling that extra queue may introduce increased latency and a slight performance penalty at the benefit of preventing link flapping. This feature must be enabled per port on specific protocols via the rx-steering option. This option takes "rss" followed by a "+" separated list of protocol names. It is only supported on ethernet ports. This feature is experimental. If the user has already configured multiple Rx queues on the port, an additional one will be allocated for packets. If the hardware cannot satisfy the requested number of requested Rx queues, the last Rx queue will be assigned for control plane. If only one Rx queue is available, the rx-steering feature will be disabled. If the hardware does not support the RTE flow matchers/actions, the feature will be disabled. It cannot be enabled when other_config:hw-offload=true as it may conflict with the offloaded RTE flows. Similarly, if hw-offload is enabled, custom rx-steering will be forcibly disabled on all ports. Example use: ovs-vsctl add-bond br-phy bond0 phy0 phy1 -- \ set interface phy0 type=dpdk options:dpdk-devargs=:ca:00.0 -- \ set interface phy0 options:rx-steering=rss+lacp -- \ set interface phy1 type=dpdk options:dpdk-devargs=:ca:00.1 -- \ set interface phy1 options:rx-steering=rss+lacp As a starting point, only one protocol is supported: LACP. Other protocols can be added in the future. NIC compatibility should be checked. To validate that this works as intended, I used a traffic generator to generate random traffic slightly above the machine capacity at line rate on a two ports bond interface. OVS is configured to receive traffic on two VLANs and pop/push them in a br-int bridge based on tags set on patch ports. +--+ | DUT | |++| || br-int || in_port=patch10,actions=mod_dl_src:$patch11,mod_dl_dst:$tgen1,output:patch11 |||| in_port=patch11,actions=mod_dl_src:$patch10,mod_dl_dst:$tgen0,output:patch10 || patch10patch11 || |+---|---|+| || | | |+---|---|+| || patch00patch01 || || tag:10tag:20 || |||| || br-phy || default flow, action=NORMAL |||| || bond0|| balance-slb, lacp=passive, lacp-time=fast ||phy0 phy1 || |+--|-|---+| +---|-|+ | | +---|-|+ | port0 port1 | balance L3/L4, lacp=active, lacp-time=fast | lag | mode trunk VLANs 10, 20 | | |switch| | | | vlan 10vlan 20 | mode access | port2 port3 | +-|--|-+ | | +-|--|-+ | tgen0 tgen1 | Random traffic that is properly balanced | | across the bond ports in both directions. | traffic generator | +--+ Without rx-steering, the bond0 links are randomly switching to "defaulted" when one of the LACP packets sent by the switch is dropped because the RX queues are full and the PMD threads did not process them fast enough. When that happens, all traffic must go through a single link which causes above line rate traffic to be dropped. ~# ovs-appctl lacp/show-stats bond0 bond0 statistics member: phy0: TX PDUs: 347246 RX PDUs: 14865 RX Bad PDUs: 0 RX Marker Request PDUs: 0 Link Expired: 168 Link Defaulted: 0 Carrier Status Changed: 0 member: phy1: TX PDUs: 347245 RX PDUs: 14919 RX Bad PDUs: 0 RX Marker Request PDUs: 0 Link Expired: 147 Link Defaulted: 1 Carrier Status Changed: 0 When rx-steering is enabled, no LACP packet is dropped and the bond links remain enabled at all times, maximizing the throughput. Neither the "Link Expired" nor the "Link Defaulted" counters are incremented anymore. This feature may be considered as "QoS". However, it does not work by limiting the rate of traffic explicitly. It only guarantees that some protocols have a lower chance of being dropped because the PMD cores cannot keep up with regular traffic. The
