Hi
From: Ananyev, Konstantin
> Hi Matan,
>
> > > > > > > > > >>>> 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.
> > > > > > >
> > > > > > > So max_rx_pkt_len will remain max size of one packet, while
> > > > > > > max_lro_len will be max accumulate size for each LRO session?
> > > > > > >
> > > > > >
> > > > > > Yes.
> > > > > >
> > > > > > > BTW, I think that for ixgbe max lro is RTE_IPV4_MAX_PKT_LEN.
> > > > > >
> > > > > > Please see my change in drivers/net/ixgbe/ixgbe_ethdev.c.
> > > > > > Change to RTE_IPV4_MAX_PKT_LEN?
> > > > > >
> > > > > > > ixgbe_vf, as I remember, doesn’t support LRO at all.
> > > > > >
> > > > > > Please see my change in
> > > > > > drivers/net/ixgbe/ixgbe_vf_representor.c
> > > > > > Remove it?
> > > > >
> > > > > Yes, please for both.
> > > >
> > > > Will change in v5.
> > > >
> > > > >
> > > > > >
> > > > > > >
> > > > > > > >
> > > > > > > > > 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.
> > > > > > >
> > > > > > > Another question, what will happen if PMD will ignore that
> > > > > > > value and will generate packets bigger then requested?
> > > > > >
> > > > > > PMD should use this value and not ignore it.
> > > > >
> > > > > Hmm, ok but this patch updates mxl driver only...
> > > > > I suppose you expect other PMD maintainers to do the job for
> > > > > their PMDs, right?
> > > > > If so, are they aware (and agree) for this new hard requirement
> > > > > and changes required?
> > > > > Again what PMD should do if it can't support exact value?
> > > > > Let say user asked max_lro_size=20KB but PMD can do only 16KB or
> > > 24KB?
> > > > > Should it fail, or round to smallest, or ...?
> > > > >
> > > > > Actually I wonder, should it really be a hard requirement or
> > > > > more like a guidance to PMD?
> > > > > Why app needs and *exact* value for LRO size?
> > > >
> > > > The exact value should be configured to HW as LRO session limit.
> > >
> > > But if the HW can't support this exact value, see the example above?
> > > In fact, shouldn't we allow PMD to forbid user to configure max LRO size?
> > > Let say if in dev_info max_lro_size==0, then PMD doesn't support LRO
> > > size configuration at all.
> > > That way PMDs who do support LRO, but don't want to (can't to)
> > > support configurable LRO size will stay untouched.
> >
> > Each HW should support packet size limitation no matter if it is LRO packet
> or not:
> > How does the PMD limit the packet size for max rx packet len conf?
> > How does the PMD limit the packet size for the mbuf size?
>
> Not sure I understand your statement and questions above...
> For sure PMD has to support max_rx_pktlen., but how does it relate to
> max_lro?
You said that HW may not support LRO max size configuration.
I answered that as same as the HW can limit packets to the configuration of
max_rx_pkt_len, so it can limit LRO packets size here too.
For simplifications:
Rx Queues which are not configured to do LRO offload should limit their packets
to the max_rx_pkt_len field.
Rx Queues which are configured to do LRO offload should limit their packets to
the max_lro_pkt_len new field.
In addition, both should limit the packets size to the mbuf size of the Rx
mempool configured to the Rx queue( if scatter offload is not enabled).
