Re: Netvsc vs Failsafe Performance

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

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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

On Wed, Sep 4, 2024 at 7:30 PM Long Li <longli@microsoft.com> wrote:

> > Subject: Re: Netvsc vs Failsafe Performance
> >
> > On Tue, 3 Sep 2024 17:21:48 -0700
> > Nandini Rangaswamy <nandini.rangaswamy@broadcom.com> wrote:
> >
> > > Hi Stephen/Long,
> > > dpdk_netvsc_port_configure:1873 Configure port eth2/2. I am testing
> > > using TCP traffic (iperf3 tool) generated between pair of client and
> > > servers with DPDK app forward traffic between client and servers.
> > > These are the config being passed for configuring netvsc:
> > > lsc_intr=1
> > > rxq/txq=2/2,
> > > rss is enabled with rss_hf=0x0000000000000c30
> > > tx_ol=0x00000000000006
> > > rx_ol=0x00000000080007
> > >
> > > Rsskey len is 64.
> > > 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_UDP |
> > > 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, },
> > >
> > > Regards,
> > > Nandini
> > >
> > > On Tue, Sep 3, 2024 at 5:03 PM Stephen Hemminger
> > > <stephen@networkplumber.org>
> > > wrote:
> > >
> > > > On Tue, 3 Sep 2024 14:43:28 -0700
> > > > Nandini Rangaswamy <nandini.rangaswamy@broadcom.com> wrote:
> > > >
> > > > > Hi Stephen and Long,
> > > > > I was going through one of the netvsc patches
> > > > > https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2F
> > > > > mails.dpdk.org%2Farchives%2Fdev%2F2018-
> > August%2F110559.html&data=0
> > > > >
> > 5%7C02%7Clongli%40microsoft.com%7Ce91cca1ee99f4809138708dccd32e76
> > 7
> > > > > %7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C638610865749
> > 361006%7
> > > > >
> > CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJB
> > TiI
> > > > >
> > 6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=ms6yhMjBpT0IFu6e9
> > wmh4K1
> > > > > WDINzgjoRzFJmMJGJwuY%3D&reserved=0 which
> > > > mentioned
> > > > > that netvsc and failsafe give the same performance in VF path
> > > > > whereas for some exception path  tests, about 22% performance gain
> in
> > seen.
> > > > > I ran some tests locally with my dpdk app integrated with netvsc
> > > > > PMD and observed that netvsc does give nearly the same performance
> > > > > as failsafe in the VF path.
> > > > > Since the official document does not explicitly cite this, I would
> > > > > like
> > > > to
> > > > > confirm if this holds good.
> > > > > Regards,
> > > > > Nandini
> > > > >
> > > >
> > > > Shouldn't be. What settings are you using.
> > > > Both failsafe and netvsc just pass packets to VF if present.
> > > > There is even more locks to go through with failsafe.
> > > >
> > > > Are you sure the test doesn't exercise something like checksumming
> > > > which maybe different.
> > > >
> > >
> >
> > How many streams? RSS won't matter unless multiple streams.
> > The netvsc driver does not have RSS for UDP as a listed flag.
> > It turns out that for that version of NDIS, if you ask for TCP RSS, UDP
> RSS is
> > implied.
> >
> > RSS Key must be 40 bytes (Toeplitz) not 64 bytes.
> > Just use the default key (rss_key == NULL rss_key_len = 0) to be safe
> >
> > Check that packets are going to the VF. One way to do that is to look at
> xstats
> > on both netvsc and mlx5 device.
> >
>
> If most traffic goes through the VF, you won't see much difference in
> performance of netvsc vs failsafe because they are not used on the data
> path.
>
> It seems the 20% performance gain is measured on synthetic path, meaning
> those traffic does not go through the VF. In this scenario, netvsc has an
> advantage over failsafe since the traffic data doesn't need to be copied
> around in the kernel space.
>

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