> -----Original Message----- > From: Chengchang Tang <tangchengch...@huawei.com> > Sent: Tuesday, April 20, 2021 1:44 PM > To: Ananyev, Konstantin <konstantin.anan...@intel.com>; Yigit, Ferruh > <ferruh.yi...@intel.com>; dev@dpdk.org > Cc: linux...@huawei.com; ch...@att.com; humi...@huawei.com > Subject: Re: [dpdk-dev] [RFC 0/2] add Tx prepare support for bonding device > > Hi > On 2021/4/20 16:33, Ananyev, Konstantin wrote: > > Hi everyone, > > > >> > >> On 2021/4/20 9:26, Ferruh Yigit wrote: > >>> On 4/16/2021 12:04 PM, Chengchang Tang wrote: > >>>> This patch add Tx prepare for bonding device. > >>>> > >>>> Currently, the bonding driver has not implemented the callback of > >>>> rte_eth_tx_prepare function. Therefore, the TX prepare function of the > >>>> slave devices will never be invoked. When hardware offloading such as > >>>> CKSUM and TSO are enabled for some drivers, tx_prepare needs to be used > >>>> to adjust packets (for example, set correct pseudo packet headers). > >>>> Otherwise, related offloading fails and even packets are sent > >>>> incorrectly. Due to this limitation, the bonded device cannot use these > >>>> HW offloading in the Tx direction. > >>>> > >>>> Because packet sending algorithms are numerous and complex in bond PMD, > >>>> it is hard to design the callback for rte_eth_tx_prepare. In this patch, > >>>> the tx_prepare callback of bonding PMD is not implemented. Instead, > >>>> rte_eth_tx_prepare has been called in tx_burst callback. And a global > >>>> variable is introduced to control whether the bonded device need call > >>>> the rte_eth_tx_prepare. If upper-layer users need to use some TX > >>>> offloading that depend on tx_prepare , they should enable the preparation > >>>> function. In this way, the bonded device will call the rte_eth_tx_prepare > >>>> for the fast path packets in the tx_burst callback. > > > > I admit that I didn't look at the implementation yet, but it sounds like > > overcomplication to me. Can't we just have a new TX function for bonding PMD > > when TX offloads are enabled? And inside that function we will do: > > tx_prepare(); tx_burst(); for selected device. > > The solution you mentioned is workable and may perform better. However, the > current > solution is also simple and has a limited impact on performance. It is > actually: > if (tx_prepare_enable) > tx_prepare(); > tx_burst(); > > Overall, it adds almost only one judgment to the case where the related Tx > offloads > is not turned on. > > > We can select this function at setup stage analysing requested by user TX > > offloads. > > > > In PMDs, it is a common practice to select different Tx/Rx function during > the setup > phase. But for a 'vdev' device like Bonding, we may need to think more about > it. > The reasons are explained below. > > > >>>> > >>> > >>> What do you think to add a devarg to bonding PMD to control the > >>> tx_prepare? > >>> It won't be as dynamic as API, since it can be possible to change the > >>> behavior after application is started with API, but do we really need > >> this? > >> > >> If an API is not added, unnecessary constraints may be introduced. If the > >> bonding device is created through the rte_eth_bond_create interface instead > >> devarg "vdev", this function cannot be used because devargs does not take > >> effect > >> in this case. But from an ease-of-use perspective, adding a devarg is a > >> good > >> idea. I will add related implementations in the later official patches. > > > > I am also against introducing new devarg to control tx_prepare() invocation. > > I think at dev_config/queue_setup phase PMD will have enough information to > > decide. > > > Currently, the community does not specify which Tx offloads need to invoke > tx_prepare.
I think inside bond PMD we can safely assume that any TX offload does need tx_prepare(). If that's not the case then slave dev tx_prepare pointer will be NULL and rte_eth_tx_prepare() will be just a NOOP. > For Vdev devices such as bond, all NIC devices need to be considered. > Generally, > tx_prepare is used in CKSUM and TSO. It is possible that for some NIC > devices, even > CKSUM and TSO do not need to invoke tx_prepare, or for some NIC devices, > there are > other Tx offloads that need to call tx_prepare. From this perspective, > leaving the > choice to the user seems to be a better choice. Wonder how user will know when to enable/disable it? As you said it depends on the underlying HW/PMD and can change from system to system? I think it is PMD that needs to take this decision, and I think the safest bet might be to enable it when any TX offloads was enabled by user. > >> > >> If I understand correctly, the current community does not want to introduce > >> more private APIs for PMDs. However, the absence of an API on this issue > >> would > >> introduce some unnecessary constraints, and from that point of view, I > >> think > >> adding an API seems necessary. > >>> > >>>> Chengchang Tang (2): > >>>> net/bonding: add Tx prepare for bonding > >>>> app/testpmd: add cmd for bonding Tx prepare > >>>> > >>>> app/test-pmd/cmdline.c | 66 > >>>> +++++++++++++++++++++++++++++ > >>>> doc/guides/testpmd_app_ug/testpmd_funcs.rst | 9 ++++ > >>>> drivers/net/bonding/eth_bond_private.h | 1 + > >>>> drivers/net/bonding/rte_eth_bond.h | 29 +++++++++++++ > >>>> drivers/net/bonding/rte_eth_bond_api.c | 28 ++++++++++++ > >>>> drivers/net/bonding/rte_eth_bond_pmd.c | 33 +++++++++++++-- > >>>> drivers/net/bonding/version.map | 5 +++ > >>>> 7 files changed, 167 insertions(+), 4 deletions(-) > >>>> > >>>> -- > >>>> 2.7.4 > >>>> > >>> > >>> > >>> . > >>> > >
