Hi Konstantin From: Ananyev, Konstantin > Sent: Friday, November 8, 2019 6:29 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. > > 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?