On 11/24/20 8:46 PM, Ferruh Yigit wrote: > On 11/3/2020 9:07 AM, Yang, SteveX wrote: >>> -----Original Message----- >>> From: Ananyev, Konstantin <konstantin.anan...@intel.com> >>> Sent: Tuesday, November 3, 2020 12:05 AM >>> To: Yigit, Ferruh <ferruh.yi...@intel.com>; Andrew Rybchenko >>> <andrew.rybche...@oktetlabs.ru>; Yang, SteveX <stevex.y...@intel.com>; >>> dev@dpdk.org >>> Cc: Xing, Beilei <beilei.x...@intel.com>; Lu, Wenzhuo >>> <wenzhuo...@intel.com>; Iremonger, Bernard >>> <bernard.iremon...@intel.com>; Yang, Qiming <qiming.y...@intel.com>; >>> m...@ashroe.eu; nhor...@tuxdriver.com >>> Subject: RE: [dpdk-dev] [PATCH v8 2/2] doc: annouce deprecation of jumbo >>> frame flag condition >>> >>>> On 11/2/2020 1:18 PM, Andrew Rybchenko wrote: >>>>> On 11/2/20 11:52 AM, SteveX Yang wrote: >>>>>> Annouce to replace 'RTE_ETHER_MAX_LEN' with 'RTE_ETHER_MTU' as type >>>>>> condition of jumbo frame. Involved scopes: >>>>>> - rte_ethdev; >>>>>> - app, e.g.: test-pmd, test-eventdev; >>>>>> - examples, e.g.: ipsec-secgw, l3fwd, vhost; >>>>>> - net PMDs which support VLAN tag(s) within overhead, e.g.: i40e, >>>>>> ixgbe; >>>>>> >>>>>> Signed-off-by: SteveX Yang <stevex.y...@intel.com> >>>>>> --- >>>>>> doc/guides/rel_notes/deprecation.rst | 12 ++++++++++++ >>>>>> 1 file changed, 12 insertions(+) >>>>>> >>>>>> diff --git a/doc/guides/rel_notes/deprecation.rst >>>>>> b/doc/guides/rel_notes/deprecation.rst >>>>>> index 2e082499b..fae139f01 100644 >>>>>> --- a/doc/guides/rel_notes/deprecation.rst >>>>>> +++ b/doc/guides/rel_notes/deprecation.rst >>>>>> @@ -138,6 +138,18 @@ Deprecation Notices >>>>>> will be limited to maximum 256 queues. >>>>>> Also compile time flag ``RTE_ETHDEV_QUEUE_STAT_CNTRS`` will be >>>>>> removed. >>>>>> +* ethdev: Offload flag ``DEV_RX_OFFLOAD_JUMBO_FRAME`` will be set >>>>>> +according to >>>>>> + ``RTE_ETHER_MTU`` in next release. Currently, the jumbo frame >>>>>> +uses the >>>>>> + ``RTE_ETHER_MAX_LEN`` as boundary condition. When the MTU (1500) >>>>>> +set, the >>>>>> + frame type of rx packet will be different if used different >>>>>> +overhead, it will >>>>>> + cause the consistency issue. Hence, using fixed value >>>>>> +``RTE_ETHER_MTU`` can >>>>>> + avoid this issue. >>>>>> + Following scopes will be changed: >>>>>> + - ``rte_ethdev`` >>>>>> + - ``app``, e.g.: ``test-pmd``, ``test-eventdev``; >>>>>> + - ``examples``, e.g.: ``ipsec-secgw``, ``l3fwd``, ``vhost``; >>>>>> + - net PMDs which support VLAN tag(s) within overhead, e.g.: >>>>>> +``i40e``; >>>>>> + >>>>>> * cryptodev: support for using IV with all sizes is added, J0 >>>>>> still can >>>>>> be used but only when IV length in following structs >>>>>> ``rte_crypto_auth_xform``, >>>>>> ``rte_crypto_aead_xform`` is set to zero. When IV length is >>>>>> greater or equal >>>>>> >>>>> >>>>> If so, what's the point to have the offload? May be just deprecate >>>>> and later remove it? >>>>> >>> >>> Same thought actually, can we remove DEV_RX_OFFLOAD_JUMBO_FRAME >>> flag completely? >>> PMD can decide based on provided MTU size does segmentation, etc. is >>> needed. >>> >> >> Yes, it seems can be removed when base on MTU size. >> I've checked related code of using DEV_RX_OFFLOAD_JUMBO_FRAME. >> Most of them use for checking boundary of max packet length and set >> 'dev->data->mtu'. >> > > Steve already sent the RFC for above fix: > https://patches.dpdk.org/patch/84486/ > > We can consider removing 'DEV_RX_OFFLOAD_JUMBO_FRAME' but anyway it is > for 21.11. > > This deprecation notice is required to fix the ethdev in next release, > as in the above RFC. > > I cc'ed a few more relevant people, can you please review this > deprecation notice. > > Thanks, > ferruh > > >>>> >>>> Above just changes the condition of what is called jumbo frame, nothing >>>> more. >>>> >>>> ethdev assumes max frame size (without jumbo frame support) can be >>>> 'RTE_ETHER_MAX_LEN' (1518) >>>> >>>> But a PMD can support double VLAN, and it can have RTE_ETHER_MAX_LEN + >>>> 8 bytes frame size and still may not support jumbo frame. >>>> >>>> In that case ethdev overwrites the frame size as RTE_ETHER_MAX_LEN, >>>> and this will reduce the supported MTU to 1492 (instead of expected >>>> 1500). >>>> Above deprecation notice is to fix this.
My problem with the deprecation notice is that I don't actually understand what will be done to address it. The idea explained by Ferruh in details makes sense. But I don't understand how the deprecation notice description corresponding to it. I read "Offload flag ``DEV_RX_OFFLOAD_JUMBO_FRAME`` will be set.." as an enforcement of the offload flag based on other parameters. I think it is incorrect. Or I still don't understand something... Looking at [1] adds more confusion since I don't understand why we care about dev_conf->rxmode.max_rx_pkt_len when JUMBO_FRAME offload is disabled. As far as I know JUMBO_FRAME offload enable means that driver should take a look at it and apply. Otherwise, just ignore it. [1] http://lxr.dpdk.org/dpdk/v20.08/source/lib/librte_ethdev/rte_ethdev.c#L1345
