On 11/8/2019 11:56 AM, Matan Azrad wrote:
>
>
> From: Ferruh Yigit
>> On 11/8/2019 10:10 AM, Matan Azrad wrote:
>>>
>>>
>>> From: Ferruh Yigit
>>>> On 11/8/2019 6:54 AM, Matan Azrad wrote:
>>>>> Hi
>>>>>
>>>>> From: Ferruh Yigit
>>>>>> On 11/7/2019 12:35 PM, Dekel Peled wrote:
>>>>>>> @@ -1266,6 +1286,18 @@ struct rte_eth_dev *
>>>>>>>
>>>>>> RTE_ETHER_MAX_LEN;
>>>>>>> }
>>>>>>>
>>>>>>> + /*
>>>>>>> + * If LRO is enabled, check that the maximum aggregated
>> packet
>>>>>>> + * size is supported by the configured device.
>>>>>>> + */
>>>>>>> + if (dev_conf->rxmode.offloads &
>> DEV_RX_OFFLOAD_TCP_LRO) {
>>>>>>> + ret = check_lro_pkt_size(
>>>>>>> + port_id, dev_conf-
>>>>>>> rxmode.max_lro_pkt_size,
>>>>>>> + dev_info.max_lro_pkt_size);
>>>>>>> + if (ret != 0)
>>>>>>> + goto rollback;
>>>>>>> + }
>>>>>>> +
>>>>>>
>>>>>> This check forces applications that enable LRO to provide
>>>> 'max_lro_pkt_size'
>>>>>> config value.
>>>>>
>>>>> Yes.(we can break an API, we noticed it)
>>>>
>>>> I am not talking about API/ABI breakage, that part is OK.
>>>> With this check, if the application requested LRO offload but not
>>>> provided 'max_lro_pkt_size' value, device configuration will fail.
>>>>
>>> Yes
>>>> Can there be a case application is good with whatever the PMD can
>>>> support as max?
>>> Yes can be - you know, we can do everything we want but it is better to be
>> consistent:
>>> Due to the fact of Max rx pkt len field is mandatory for JUMBO offload, max
>> lro pkt len should be mandatory for LRO offload.
>>>
>>> So your question is actually why both, non-lro packets and LRO packets max
>> size are mandatory...
>>>
>>>
>>> I think it should be important values for net applications management.
>>> Also good for mbuf size managements.
>>>
>>>>>
>>>>>> - Why it is mandatory now, how it was working before if it is
>>>>>> mandatory value?
>>>>>
>>>>> It is the same as max_rx_pkt_len which is mandatory for jumbo frame
>>>> offload.
>>>>> So now, when the user configures a LRO offload he must to set max
>>>>> lro pkt
>>>> len.
>>>>> We don't want to confuse the user here with the max rx pkt len
>>>> configurations and behaviors, they should be with same logic.
>>>>>
>>>>> This parameter defines well the LRO behavior.
>>>>> Before this, each PMD took its own interpretation to what should be
>>>>> the
>>>> maximum size for LRO aggregated packets.
>>>>> Now, the user must say what is his intension, and the ethdev can
>>>>> limit it
>>>> according to the device capability.
>>>>> By this way, also, the PMD can organize\optimize its data-path more.
>>>>> Also, the application can create different mempools for LRO queues
>>>>> to
>>>> allow bigger packet receiving for LRO traffic.
>>>>>
>>>>>> - What happens if PMD doesn't provide 'max_lro_pkt_size', so it is '0'?
>>>>> Yes, you can see the feature description Dekel added.
>>>>> This patch also updates all the PMDs support an LRO for non-0 value.
>>>>
>>>> Of course I can see the updates Matan, my point is "What happens if
>>>> PMD doesn't provide 'max_lro_pkt_size'",
>>>> 1) There is no check for it right, so it is acceptable?
>>>
>>> There is check.
>>> If the capability is 0, any non-zero configuration will fail.
>>>
>>>> 2) Are we making this filed mandatory to provide for PMDs, it is easy
>>>> to make new fields mandatory for PMDs but is this really necessary?
>>>
>>> Yes, for consistence.
>>>
>>>>>
>>>>> as same as max rx pkt len, no?
>>>>>
>>>>>> - What do you think setting 'max_lro_pkt_size' config value to what
>>>>>> PMD provided if application doesn't provide it?
>>>>> Same answers as above.
>>>>>
>>>>
>>>> If application doesn't care the value, as it has been till now, and
>>>> not provided explicit 'max_lro_pkt_size', why not ethdev level use
>>>> the value provided by PMD instead of failing?
>>>
>>> Again, same question we can ask on max rx pkt len.
>>>
>>> Looks like the packet size is very important value which should be set by
>> the application.
>>>
>>> Previous applications have no option to configure it, so they haven't
>> configure it, (probably cover it somehow) I think it is our miss to supply
>> this
>> info.
>>>
>>> Let's do it in same way as we do max rx pkt len (as this patch main idea).
>>> Later, we can change both to other meaning.
>>>
>>
>> I think it is not a good reason to introduce a new mandatory config option
>> for
>> application because of 'max_rx_pkt_len' does it.
>
> It is mandatory only if LRO offload is configured.
>
>> Will it work, if:
>> - If application doesn't provide this value, use the PMD max
>
> May cause a problem if the mbuf size is not enough for the PMD maximum.
OK, this is what I was missing, for this case I was thinking max_rx_pkt_len will
be used but you already explained that application may want to use different
mempools for LRO queues.
For this case shouldn't PMDs take the 'rxmode.max_lro_pkt_size' into account and
program the device accordingly (of course in LRO enabled case) ?
This part seems missing and should be highlighted to other PMD maintainers.
>
>> - If both application and PMD doesn't provide this value, fail on
>> configure()?
>
> It will work.
> In my opinion - not ideal.
>
> Matan
>
>
