From: Ferruh Yigit
> On 11/8/2019 10:10 AM, Matan Azrad wrote:
> >
> >
> > From: Ferruh Yigit
> >> On 11/8/2019 6:54 AM, Matan Azrad wrote:
> >>> Hi
> >>>
> >>> From: Ferruh Yigit
> >>>> On 11/7/2019 12:35 PM, Dekel Peled wrote:
> >>>>> @@ -1266,6 +1286,18 @@ struct rte_eth_dev *
> >>>>>
> >>>> RTE_ETHER_MAX_LEN;
> >>>>> }
> >>>>>
> >>>>> + /*
> >>>>> + * If LRO is enabled, check that the maximum aggregated
> packet
> >>>>> + * size is supported by the configured device.
> >>>>> + */
> >>>>> + if (dev_conf->rxmode.offloads &
> DEV_RX_OFFLOAD_TCP_LRO) {
> >>>>> + ret = check_lro_pkt_size(
> >>>>> + port_id, dev_conf-
> >>>>> rxmode.max_lro_pkt_size,
> >>>>> + dev_info.max_lro_pkt_size);
> >>>>> + if (ret != 0)
> >>>>> + goto rollback;
> >>>>> + }
> >>>>> +
> >>>>
> >>>> This check forces applications that enable LRO to provide
> >> 'max_lro_pkt_size'
> >>>> config value.
> >>>
> >>> Yes.(we can break an API, we noticed it)
> >>
> >> I am not talking about API/ABI breakage, that part is OK.
> >> With this check, if the application requested LRO offload but not
> >> provided 'max_lro_pkt_size' value, device configuration will fail.
> >>
> > Yes
> >> Can there be a case application is good with whatever the PMD can
> >> support as max?
> > Yes can be - you know, we can do everything we want but it is better to be
> consistent:
> > Due to the fact of Max rx pkt len field is mandatory for JUMBO offload, max
> lro pkt len should be mandatory for LRO offload.
> >
> > So your question is actually why both, non-lro packets and LRO packets max
> size are mandatory...
> >
> >
> > I think it should be important values for net applications management.
> > Also good for mbuf size managements.
> >
> >>>
> >>>> - Why it is mandatory now, how it was working before if it is
> >>>> mandatory value?
> >>>
> >>> It is the same as max_rx_pkt_len which is mandatory for jumbo frame
> >> offload.
> >>> So now, when the user configures a LRO offload he must to set max
> >>> lro pkt
> >> len.
> >>> We don't want to confuse the user here with the max rx pkt len
> >> configurations and behaviors, they should be with same logic.
> >>>
> >>> This parameter defines well the LRO behavior.
> >>> Before this, each PMD took its own interpretation to what should be
> >>> the
> >> maximum size for LRO aggregated packets.
> >>> Now, the user must say what is his intension, and the ethdev can
> >>> limit it
> >> according to the device capability.
> >>> By this way, also, the PMD can organize\optimize its data-path more.
> >>> Also, the application can create different mempools for LRO queues
> >>> to
> >> allow bigger packet receiving for LRO traffic.
> >>>
> >>>> - What happens if PMD doesn't provide 'max_lro_pkt_size', so it is '0'?
> >>> Yes, you can see the feature description Dekel added.
> >>> This patch also updates all the PMDs support an LRO for non-0 value.
> >>
> >> Of course I can see the updates Matan, my point is "What happens if
> >> PMD doesn't provide 'max_lro_pkt_size'",
> >> 1) There is no check for it right, so it is acceptable?
> >
> > There is check.
> > If the capability is 0, any non-zero configuration will fail.
> >
> >> 2) Are we making this filed mandatory to provide for PMDs, it is easy
> >> to make new fields mandatory for PMDs but is this really necessary?
> >
> > Yes, for consistence.
> >
> >>>
> >>> as same as max rx pkt len, no?
> >>>
> >>>> - What do you think setting 'max_lro_pkt_size' config value to what
> >>>> PMD provided if application doesn't provide it?
> >>> Same answers as above.
> >>>
> >>
> >> If application doesn't care the value, as it has been till now, and
> >> not provided explicit 'max_lro_pkt_size', why not ethdev level use
> >> the value provided by PMD instead of failing?
> >
> > Again, same question we can ask on max rx pkt len.
> >
> > Looks like the packet size is very important value which should be set by
> the application.
> >
> > Previous applications have no option to configure it, so they haven't
> configure it, (probably cover it somehow) I think it is our miss to supply
> this
> info.
> >
> > Let's do it in same way as we do max rx pkt len (as this patch main idea).
> > Later, we can change both to other meaning.
> >
>
> I think it is not a good reason to introduce a new mandatory config option for
> application because of 'max_rx_pkt_len' does it.
It is mandatory only if LRO offload is configured.
> Will it work, if:
> - If application doesn't provide this value, use the PMD max
May cause a problem if the mbuf size is not enough for the PMD maximum.
> - If both application and PMD doesn't provide this value, fail on configure()?
It will work.
In my opinion - not ideal.
Matan
