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.
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.
>>
>> 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
>>>>
>>>
>>>
>>> .
>>>
>
