Re: [dpdk-dev] [PATCH 2/2] net/bonding: support configuring Tx offloading for bonding

[Chengchang Tang <tangchengchang@huawei.com>]

Hi, Andrew and Ananyev

On 2021/6/9 17:37, Andrew Rybchenko wrote:
> On 6/9/21 12:11 PM, Ananyev, Konstantin wrote:
>>
>>>
>>>
>>> On 2021/6/8 17:49, Andrew Rybchenko wrote:
>>>> "for bonding" is redundant in the summary since it is already
>>>> "net/bonding"
>>>>
>>>> On 4/23/21 12:46 PM, Chengchang Tang wrote:
>>>>> Currently, the TX offloading of the bonding device will not take effect by
>>>>
>>>> TX -> Tx
>>>>
>>>>> using dev_configure. Because the related configuration will not be
>>>>> delivered to the slave devices in this way.
>>>>
>>>> I think it is a major problem that Tx offloads are actually
>>>> ignored. It should be a patches with "Fixes:" which addresses
>>>> it.
>>>>
>>>>> The Tx offloading capability of the bonding device is the intersection of
>>>>> the capability of all slave devices. Based on this, the following functions
>>>>> are added to the bonding driver:
>>>>> 1. If a Tx offloading is within the capability of the bonding device (i.e.
>>>>> all the slave devices support this Tx offloading), the enabling status of
>>>>> the offloading of all slave devices depends on the configuration of the
>>>>> bonding device.
>>>>>
>>>>> 2. For the Tx offloading that is not within the Tx offloading capability
>>>>> of the bonding device, the enabling status of the offloading on the slave
>>>>> devices is irrelevant to the bonding device configuration. And it depends
>>>>> on the original configuration of the slave devices.
>>>>>
>>>>> Signed-off-by: Chengchang Tang <tangchengchang@huawei.com>
>>>>> ---
>>>>>  drivers/net/bonding/rte_eth_bond_pmd.c | 13 +++++++++++++
>>>>>  1 file changed, 13 insertions(+)
>>>>>
>>>>> diff --git a/drivers/net/bonding/rte_eth_bond_pmd.c b/drivers/net/bonding/rte_eth_bond_pmd.c
>>>>> index 84af348..9922657 100644
>>>>> --- a/drivers/net/bonding/rte_eth_bond_pmd.c
>>>>> +++ b/drivers/net/bonding/rte_eth_bond_pmd.c
>>>>> @@ -1712,6 +1712,8 @@ slave_configure(struct rte_eth_dev *bonded_eth_dev,
>>>>>  	struct rte_flow_error flow_error;
>>>>>
>>>>>  	struct bond_dev_private *internals = bonded_eth_dev->data->dev_private;
>>>>> +	uint64_t tx_offload_cap = internals->tx_offload_capa;
>>>>> +	uint64_t tx_offload;
>>>>>
>>>>>  	/* Stop slave */
>>>>>  	errval = rte_eth_dev_stop(slave_eth_dev->data->port_id);
>>>>> @@ -1759,6 +1761,17 @@ slave_configure(struct rte_eth_dev *bonded_eth_dev,
>>>>>  		slave_eth_dev->data->dev_conf.rxmode.offloads &=
>>>>>  				~DEV_RX_OFFLOAD_JUMBO_FRAME;
>>>>>
>>>>> +	while (tx_offload_cap != 0) {
>>>>> +		tx_offload = 1ULL << __builtin_ctzll(tx_offload_cap);
>>>>> +		if (bonded_eth_dev->data->dev_conf.txmode.offloads & tx_offload)
>>>>> +			slave_eth_dev->data->dev_conf.txmode.offloads |=
>>>>> +				tx_offload;
>>>>> +		else
>>>>> +			slave_eth_dev->data->dev_conf.txmode.offloads &=
>>>>> +				~tx_offload;
>>>>> +		tx_offload_cap &= ~tx_offload;
>>>>> +	}
>>>>> +
>>>>
>>>> Frankly speaking I don't understand why it is that complicated.
>>>> ethdev rejects of unsupported Tx offloads. So, can't we simply:
>>>> slave_eth_dev->data->dev_conf.txmode.offloads =
>>>>     bonded_eth_dev->data->dev_conf.txmode.offloads;
>>>>
>>>
>>> Using such a complicated method is to increase the flexibility of the slave devices,
>>> allowing the Tx offloading of the slave devices to be incompletely consistent with
>>> the bond device. If some offloading can be turned on without bond device awareness,
>>> they can be retained in this case.
>>
>>
>> Not sure how that can that happen...
> 
> +1
> 
> @Chengchang could you provide an example how it could happen.
> 

For example:
device 1 capability: VLAN_INSERT | MBUF_FAST_FREE
device 2 capability: VLAN_INSERT
And the capability of bonded device will be VLAN_INSERT.
So, we can only set VLAN_INSERT for the bonded device. So what if we want to enable
MBUF_FAST_FREE in device 1 to improve performance? For the application, as long as it
can guarantee the condition of MBUF ref_cnt = 1, then it can run normally if
MBUF_FAST_FREE is turned on.

In my logic, if device 1 has been configured with MBUF_FAST_FREE, and then
added to the bonded device as a slave. The MBUF_FAST_FREE will be reserved.

>> From my understanding tx_offload for bond device has to be intersection of tx_offloads
>> of all slaves, no? Otherwise bond device might be misconfigured.
>> Anyway for that code snippet above, wouldn't the same be achived by:
>> slave_eth_dev->data->dev_conf.txmode.offloads &= internals->tx_offload_capa & bonded_eth_dev->data->dev_conf.txmode.offloads;
>> ?
> 

I think it will not achieved my purpose in the scenario I mentioned above.

> .
>