Thanks, PSB.
> -----Original Message-----
> From: Ananyev, Konstantin <konstantin.anan...@intel.com>
> Sent: Friday, November 8, 2019 4:53 PM
> To: Dekel Peled <dek...@mellanox.com>; Matan Azrad
> <ma...@mellanox.com>; Yigit, Ferruh <ferruh.yi...@intel.com>; Mcnamara,
> John <john.mcnam...@intel.com>; Kovacevic, Marko
> <marko.kovace...@intel.com>; nhor...@tuxdriver.com;
> ajit.khapa...@broadcom.com; somnath.ko...@broadcom.com; Burakov,
> Anatoly <anatoly.bura...@intel.com>; xuanziya...@huawei.com;
> cloud.wangxiao...@huawei.com; zhouguoy...@huawei.com; Lu, Wenzhuo
> <wenzhuo...@intel.com>; Shahaf Shuler <shah...@mellanox.com>; Slava
> Ovsiienko <viachesl...@mellanox.com>; rm...@marvell.com;
> shsha...@marvell.com; maxime.coque...@redhat.com; Bie, Tiwei
> <tiwei....@intel.com>; Wang, Zhihong <zhihong.w...@intel.com>;
> yongw...@vmware.com; Thomas Monjalon <tho...@monjalon.net>;
> arybche...@solarflare.com; Wu, Jingjing <jingjing...@intel.com>;
> Iremonger, Bernard <bernard.iremon...@intel.com>
> Cc: dev@dpdk.org
> Subject: RE: [dpdk-dev] [PATCH v4 1/3] ethdev: support API to set max LRO
> packet size
>
>
> > > > > >>>> 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.
>
>
> > >
> > > >
> > > > > - If both application and PMD doesn't provide this value, fail
> > > > > on
> > > configure()?
> > > >
> > > > It will work.
> > > > In my opinion - not ideal.
> > > >
> > > > Matan
> > > >
