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

[Ananyev, Konstantin]

> 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 at 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.

So your intention is to allow slave device silently overrule master tx_offload settings?
If so, I don't think it is a good idea - sounds like potentially bogus and error prone approach.
Second thing - I still don't see how the code above can help you with it.
From what I read in your code - you clear tx_offload bits that are not not supported by the master.

> 
> >> 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.
> 
> > .
> >