[dpdk-dev] [PATCH] ethdev: rte_eth_rx_burst() nb_pkts requirements

[Ferruh Yigit]

On 10/27/2020 10:24 AM, Bruce Richardson wrote:
> On Mon, Sep 14, 2020 at 01:05:11PM +0200, Morten Brørup wrote:
>> Updated description of rte_eth_rx_burst() to reflect what drivers,
>> when using vector instructions, expect from nb_pkts.
>>
>> Also discussed on the mailing list here:
>> http://inbox.dpdk.org/dev/98CBD80474FA8B44BF855DF32C47DC35C61257@smartserver.smartshare.dk/
>>
>> Signed-off-by: Morten Brørup <mb at smartsharesystems.com>
>> ---
>>   lib/librte_ethdev/rte_ethdev.h | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/lib/librte_ethdev/rte_ethdev.h b/lib/librte_ethdev/rte_ethdev.h
>> index 70295d7ab..41f8ba4ef 100644
>> --- a/lib/librte_ethdev/rte_ethdev.h
>> +++ b/lib/librte_ethdev/rte_ethdev.h
>> @@ -4469,6 +4469,10 @@ int rte_eth_dev_hairpin_capability_get(uint16_t port_id,
>>    * burst-oriented optimizations in both synchronous and asynchronous
>>    * packet processing environments with no overhead in both cases.
>>    *
>> + * @note
>> + *   Some drivers using vector instructions require that *nb_pkts* is
>> + *   divisible by 4 or 8, depending on the driver implementation.
>> + *
>>    * The rte_eth_rx_burst() function does not provide any error
>>    * notification to avoid the corresponding overhead. As a hint, the
>>    * upper-level application might check the status of the device link once
>> @@ -4485,6 +4489,7 @@ int rte_eth_dev_hairpin_capability_get(uint16_t port_id,
>>    *   must be large enough to store *nb_pkts* pointers in it.
>>    * @param nb_pkts
>>    *   The maximum number of packets to retrieve.
>> + *   The value must be divisible by 8 in order to work with any driver.
>>    * @return
>>    *   The number of packets actually retrieved, which is the number
>>    *   of pointers to *rte_mbuf* structures effectively supplied to the
>> -- 
> 
> This correctly documents the current situation, so following the discussion
> on-list:
> 
> Acked-by: Bruce Richardson <bruce.richardson at intel.com>
> 

Applied to dpdk-next-net/main, thanks.