Re: [dpdk-dev] [PATCH v4] examples/l2fwd: add cmdline option for forwarding port info

[Thomas Monjalon <thomas@monjalon.net>]

Bruce, as maintainer of l2fwd example, any opinion about this change?


11/05/2020 02:23, Pavan Nikhilesh Bhagavatula:
> Hi Vipin,
> 
> >Hi Pavan,
> >
> >snipped
> >> >
> >> >Should we check & warn the user if
> >> >1. port speed mismatch
> >> >2. on different NUMA
> >> >3. port pairs are physical and vdev like tap, and KNI (performance).
> >> >
> >>
> >> Sure, it can be a separate patch as it will be applicable for multiple
> >examples.
> >I believe this patch is for example `l2fwd`. But you would like to have to
> >updated for all `example`. I am ok for this.
> >
> >snipped
> >> >
> >> >Should not the check_port_pair be after this? If the port is not
> >> >enabled in port_mask will you skip that pair? or skip RX-TX from that
> >port?
> >>
> >> We check every port pair against l2fwd_enabled_port_mask in
> >> check_port_pair_config()
> >
> >
> >>
> >snipped
> >> >
> >> >As mentioned above there can ports in mask which might be
> >disabled for
> >> >port pair. Should not that be skipped rather than setting last port rx-
> >> >tx loopback?
> >>
> >> There could be scenarios where user might want to test 2x10G and
> >1x40G Why
> >> force the user to explicitly mention 1x40G as port pair of itself in the
> >portpair
> >> config?
> >I am not sure if I follow your thought, as your current port map only
> >allows `1:1` mapping by `struct port_pair_params`. This can be to self
> >like `(port0:port0),(port1:port1)` or `(port-0:port-1)`.
> >
> >1. But current `l2fwd_parse_port_pair_config` does not consider the
> >same port mapping as we have hard check for `if (nb_port_pair_params
> >>= RTE_MAX_ETHPORTS/2)`.
> >
> >2. `l2fwd_enabled_port_mask` is global variable of user port mask. This
> >can contain both valid and invalid mask. Hence we check
> >`l2fwd_enabled_port_mask & ~((1 << nb_ports) - 1)`.
> >
> >3. can these scenarios are true if we invoke `check_port_pair_config`
> >before actual port_mask check.
> > a. there are only 4 ports, hence possible mask is `0xf`.
> > b. user passes port argument as `0xe`
> > c. `check_port_pair_config` gets masks for `(1,3)` as input and
> >populates `port_pair_config_mask`.
> > d.  As per the code, port 2 which is valid port and part of user port mask
> >will have lastport (which is port 3)? May be I did understand the logic
> >correct. Can you help me?
> 
> Here user needs to explicitly mention (2,2) for port 2 to be setup else it 
> will be skipped. 
> If you see `check_port_pair_config` below we disable the ports that are not 
> Mentioned in portmap.
> 
> "
> check_port_pair_config(void)
> {
> 
> <snip>
> 		port_pair_config_mask |= port_pair_mask;
> 	}
> 
> 	l2fwd_enabled_port_mask &= port_pair_config_mask;
> 
> 	return 0;
> }
> "
> 
> 
> >
> >So my concerns are 1) there is no same port mapping, 2) my
> >understanding on lastport logic is not clear and 3) as per the code there
> >is 1:N but 1:1.
> >
> >Hence there should be sufficient warning to user if port are of wrong
> >speed and NUMA.
> 
> Unless the user disables stats using -T 0 option all the prints will be skipped.
> 
> >
> >Note: current speed can be fetched only if the port are started too (in
> >Fortville).
> >
> >snipped