Re: Netvsc vs Failsafe Performance

[Nandini Rangaswamy <nandini.rangaswamy@broadcom.com>]

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Thanks for clarifying the question regarding Txd size Stephen.
I tested out the RSS for TCP UDP.
As suggested , I set the TCP flags alone in RSS conf and configured the
netvsc port.

struct rte_eth_conf conf = {
.intr_conf = {
.lsc = !dpdk.lsc_intr_disable && !dpdk_if->lsc_intr_disable &&
!!(dev->data->dev_flags & RTE_ETH_DEV_INTR_LSC),
},
.rxmode = {
.mq_mode = RTE_ETH_MQ_RX_RSS,
.offloads = RTE_ETH_RX_OFFLOAD_VLAN_STRIP | RTE_ETH_RX_OFFLOAD_IPV4_CKSUM |
RTE_ETH_RX_OFFLOAD_RSS_HASH | RTE_ETH_RX_OFFLOAD_UDP_CKSUM,
},
.rx_adv_conf.rss_conf = {
.rss_hf = RTE_ETH_RSS_NONFRAG_IPV4_TCP | RTE_ETH_RSS_NONFRAG_IPV6_TCP,
.rss_key = conf_rss_key,
.rss_key_len = rss_key_len,
},
.txmode = {
.offloads = RTE_ETH_TX_OFFLOAD_UDP_CKSUM | RTE_ETH_TX_OFFLOAD_IPV4_CKSUM,
},
};
rte_eth_dev_configure(<netvsc port>, num_rxq,num_txq, &conf);
uint8_t rss_key_temp[64];
struct rte_eth_rss_conf rss_conf = {
.rss_key = rss_key_temp,
.rss_key_len = sizeof(rss_key_temp),
};
ret = rte_eth_dev_rss_hash_conf_get(<VF port>, &rss_conf);


Now the VF port RSS offloads show only TCP flags set and not UDP. I assumed
that even the UDP flags might be set. Is this expected ?

Regards,
Nandini


On Thu, Sep 12, 2024 at 4:09 PM Stephen Hemminger <
stephen@networkplumber.org> wrote:

> On Thu, 12 Sep 2024 13:47:37 -0700
> Nandini Rangaswamy <nandini.rangaswamy@broadcom.com> wrote:
>
> > Thanks for your response Long Li.
> > I see with netvsc the maximum number of Tx descriptors is restricted to
> > 4096 whereas the number of Rx descriptors is restricted to 8192.
> > But, for failsafe PMD , we see that both the number of Txd and Rxd is
> > restricted to 8192.
> > How is netvsc PMD giving the same performance as failsafe PMD ?
> >
> > Regards
>
> I think the limits there were somewhat arbitrary chose with netvsc.
> Don't remember a hard reason that would block larger sizes.
>
>
> Having really big rings won't help performance (i.e BufferBloat) and
> could a lot of memory consumption. When all heavy data traffic goes through
> the VF and that ring is different. Only DoS attacks should be impacted
> by rx/tx descriptor limits in the netvsc device. The linux driver actually
> has much smaller buffer.
>

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