[dpdk-dev] [PATCH v2] net/pcap: enable data path on secondary
Ferruh Yigit
ferruh.yigit at intel.com
Tue Nov 13 19:43:43 CET 2018
On 11/13/2018 6:27 PM, Zhang, Qi Z wrote:
> First, apologies to make this in rush since I was somehow under pressure to make pdump works in 18.11.
> I agree there is lot of things need to improve, but the strategy here is to make it work quietly and not break anything else :)
> add some comments inline.
>
>> -----Original Message-----
>> From: Thomas Monjalon [mailto:thomas at monjalon.net]
>> Sent: Tuesday, November 13, 2018 9:15 AM
>> To: Yigit, Ferruh <ferruh.yigit at intel.com>; Zhang, Qi Z <qi.z.zhang at intel.com>
>> Cc: dev at dpdk.org; Lin, Xueqin <xueqin.lin at intel.com>
>> Subject: Re: [PATCH v2] net/pcap: enable data path on secondary
>>
>> Just a quick comment:
>> There are probably some ideas to take from what was done for tap.
>
>>
>>
>> 13/11/2018 17:56, Ferruh Yigit:
>>> On 11/12/2018 4:51 PM, Qi Zhang wrote:
>>>> Private vdev on secondary is never supported by the new shared
>>>> device mode but pdump still relies on a private pcap PMD on secondary.
>>>> The patch enables pcap PMD's data path on secondary so that pdump
>>>> can work as usual.
>>>
>>> It would be great if you described the problem a little more.
>>>
>>> Private vdev was the way previously, when pdump developed, now with
>>> shared device mode on virtual devices, pcap data path in secondary is not
>> working.
>>>
>>> What exactly not working is (please correct me if I am wrong):
>>> When secondary adds a virtual device, related data transferred to
>>> primary and primary creates the device and shares device back with
>> secondary.
>>> When pcap device created in primary, pcap handlers (pointers) are
>>> process local and they are not valid for secondary process. This breaks
>> secondary.
>>>
>>> So we can't directly share the pcap handlers, but need to create a new
>>> set of handlers for secondary, that is what you are doing in this
>>> patch, although I have some comments, please check below.
>>>
>>> Since there is single storage for pcap handlers that primary and
>>> secondary shares and they can't share the handlers, you can't make
>>> both primary and secondary data path work. Also freeing handlers is
>>> another concern. What is needed is `rte_eth_dev->process_private` which
>> has been added in this release.
>
> You are right, we should prevent handler be opened in primary be corrupted during probe at secondary.
> Now, I see this problem in pcap , as an example: internals->tx_queue[i].dumper/pcap is shared but will be overwritten at secondary, we should fix them by use process_private,
>
>>>
>>>>
>>>> Signed-off-by: Qi Zhang <qi.z.zhang at intel.com>
>>>> Tested-by: Yufeng Mo <yufengx.mo at intel.com>
>>>
>>> <...>
>>>
>>>> @@ -934,6 +935,10 @@ pmd_init_internals(struct rte_vdev_device
>> *vdev,
>>>> */
>>>> (*eth_dev)->dev_ops = &ops;
>>>>
>>>> + /* store a copy of devargs for secondary process */
>>>> + strlcpy(internals->devargs, rte_vdev_device_args(vdev),
>>>> + ETH_PCAP_ARG_MAXLEN);
>>>
>>> Why we need to cover this in PMD level?
>>>
>>> Why secondary probe isn't getting devargs? Can't we fix this in eal level?
>>> It can be OK to workaround in the PMD taking account of the time of
>>> the release, but for long term I think this should be fixed in eal.
>
> Yes this is the workaround for quick fix.
> Ideally secondary process should not take care of devargs, it just attach.
> And it's better to only parse devargs on one process ( primary process), the parsed result could be stored to intermediate result in shared memory,(examples, internal->nb_rx_queue_required) so secondary process don't need to parse it again.
>>>
>>> <...>
>>>
>>>> @@ -1122,23 +1126,37 @@ pmd_pcap_probe(struct rte_vdev_device
>> *dev)
>>>> start_cycles = rte_get_timer_cycles();
>>>> hz = rte_get_timer_hz();
>>>>
>>>> - if (rte_eal_process_type() == RTE_PROC_SECONDARY) {
>>>> + if (rte_eal_process_type() == RTE_PROC_PRIMARY) {
>>>> + kvlist = rte_kvargs_parse(rte_vdev_device_args(dev),
>>>> + valid_arguments);
>>>> + if (kvlist == NULL)
>>>> + return -EINVAL;
>>>> + if (rte_kvargs_count(kvlist, ETH_PCAP_IFACE_ARG) == 1)
>>>> + nb_rx_queue = 1;
>>>> + else
>>>> + nb_rx_queue =
>>>> + rte_kvargs_count(kvlist,
>>>> + ETH_PCAP_RX_PCAP_ARG) ? 1 : 0;
>>>> + nb_tx_queue = 1;
>>>
>>> This part is wrong. pcap pmd supports multi queue, you can't hardcode
>>> the number of queues. Also for Tx why it ignores `rx_iface` argument?
>>> This is just hacking the driver for a specific use case breaking others.
>
> Previously the nb_tx_queue and nb_rx_queue is decided by pcaps.num_of_queue and dumpers.num_of_queues.
> I just can't figure out a way that we can have more than 1 queue during probe, look at below code.
>
> If ETH_PCAP_IFACE_ARG
>
> pcaps.num_of_queue = 1;
> dumpers.num_of_queue = 1;
>
> else
> is_rx_pcap = rte_kvargs_count(kvlist, ETH_PCAP_RX_PCAP_ARG) ? 1 : 0;
> pcaps.num_of_queue = 0;
> if (is_rx_pcap) {
> ret = rte_kvargs_process(kvlist, ETH_PCAP_RX_PCAP_ARG,
> &open_rx_pcap, &pcaps);
>
> // pcaps.num_of_queue = 1;
> } else {
> ret = rte_kvargs_process(kvlist, NULL,
> &rx_iface_args_process, &pcaps);
> // pcaps.num_of_queue = 0;
> }
>
> is_tx_pcap = rte_kvargs_count(kvlist, ETH_PCAP_TX_PCAP_ARG) ? 1 : 0;
> dumpers.num_of_queue = 0;
>
> if (is_tx_pcap)
> ret = rte_kvargs_process(kvlist, ETH_PCAP_TX_PCAP_ARG,
> &open_tx_pcap, &dumpers);
> // dumpers.num_of_queue = 1
> else
> ret = rte_kvargs_process(kvlist, ETH_PCAP_TX_IFACE_ARG,
> &open_tx_iface, &dumpers);
> // dumpers.num_of_queue = 1
>
> That's the same logic I applied, did I missed something, would you explain more for this?
ETH_PCAP_IFACE_ARG is "iface=xxx" usage, both Rx and Tx use the same interface,
because of implementation limitation it only supports 1 queue.
rx_pcap, rx_iface, rx_iface_in supports multiple queues, by providing them
multiple time. Like "rx_pcap=q1.pcap,rx_pcap=q2.pcap,rx_pcap=q3.pcap" will
create 3 Rx queues each having their own .pcap file. Same is valid for Tx.
rte_kvargs_process() calls callback function per argument provided, so if an
argument provided multiple times, it will call same callback multiple times,
that is why 'num_of_queue' increased in callback functions.
In high-level, pmd_pcap_probe() first parses the arguments and creates pcap
handlers based on arguments, later as a last thing creates ethdev using these
information. I am for keeping this logic, doing something different for
secondary can cause issues in edge cases not obvious at first look.
>
> Thanks
> Qi
>
>>>
>>>> + ret = pmd_init_internals(dev, nb_rx_queue,
>>>> + nb_tx_queue, ð_dev);
>>>
>>> I think it is not required to move pmd_init_internals() here.
>>> This can be done simpler, I will send a draft patch as a reply to this
>>> mail for possible solution.
>>> But again that can't be final solution, we need to use
>>> `process_private`
>>>
>>> <...>
>>>
>>
>>
>>
>>
>
More information about the dev
mailing list