RE: Netvsc vs Failsafe Performance

[Long Li <longli@microsoft.com>]

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It’s a bug in netvsc for not reporting RTE_ETH_RSS_NONFRAG_IPV6_UDP. It is implied as in the case in IPV4.

Can you try the following patch?

diff --git a/drivers/net/netvsc/hn_rndis.c b/drivers/net/netvsc/hn_rndis.c
index 1ba75ee804..fe1f04d8d9 100644
--- a/drivers/net/netvsc/hn_rndis.c
+++ b/drivers/net/netvsc/hn_rndis.c
@@ -717,6 +717,7 @@ hn_rndis_query_rsscaps(struct hn_data *hv,
        if (caps.ndis_caps & NDIS_RSS_CAP_IPV6)
                hv->rss_offloads |= RTE_ETH_RSS_IPV6
                        | RTE_ETH_RSS_NONFRAG_IPV6_TCP;
+                       | RTE_ETH_RSS_NONFRAG_IPV6_UDP;
        if (caps.ndis_caps & NDIS_RSS_CAP_IPV6_EX)
                hv->rss_offloads |= RTE_ETH_RSS_IPV6_EX
                        | RTE_ETH_RSS_IPV6_TCP_EX;


From: Nandini Rangaswamy <nandini.rangaswamy@broadcom.com>
Sent: Friday, September 13, 2024 10:56 AM
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: Long Li <longli@microsoft.com>; users@dpdk.org
Subject: Re: Netvsc vs Failsafe Performance

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<mailto:stephen@networkplumber.org>> wrote:
On Thu, 12 Sep 2024 13:47:37 -0700
Nandini Rangaswamy <nandini.rangaswamy@broadcom.com<mailto: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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