On 8/6/2020 5:29 PM, Slava Ovsiienko wrote:
>> -----Original Message-----
>> From: Ferruh Yigit <ferruh.yi...@intel.com>
>> Sent: Thursday, August 6, 2020 19:16
>> To: Andrew Rybchenko <arybche...@solarflare.com>; Slava Ovsiienko
>> <viachesl...@mellanox.com>; dev@dpdk.org
>> Cc: Matan Azrad <ma...@mellanox.com>; Raslan Darawsheh
>> <rasl...@mellanox.com>; Thomas Monjalon <tho...@monjalon.net>;
>> jerinjac...@gmail.com; step...@networkplumber.org;
>> ajit.khapa...@broadcom.com; maxime.coque...@redhat.com;
>> olivier.m...@6wind.com; david.march...@redhat.com
>> Subject: Re: [PATCH] doc: announce changes to ethdev rxconf structure
>>
>> On 8/3/2020 3:31 PM, Andrew Rybchenko wrote:
>>> On 8/3/20 1:58 PM, Viacheslav Ovsiienko wrote:
>>>> The DPDK datapath in the transmit direction is very flexible.
>>>> The applications can build multisegment packets and manages almost
>>>> all data aspects - the memory pools where segments are allocated
>>>> from, the segment lengths, the memory attributes like external,
>>>> registered, etc.
>>>>
>>>> In the receiving direction, the datapath is much less flexible, the
>>>> applications can only specify the memory pool to configure the
>>>> receiving queue and nothing more. In order to extend the receiving
>>>> datapath capabilities it is proposed to add the new fields into
>>>> rte_eth_rxconf structure:
>>>>
>>>> struct rte_eth_rxconf {
>>>> ...
>>>> uint16_t rx_split_num; /* number of segments to split */
>>>> uint16_t *rx_split_len; /* array of segment lengthes */
>>>> struct rte_mempool **mp; /* array of segment memory pools */
>>>> ...
>>>> };
>>>>
>>>> The non-zero value of rx_split_num field configures the receiving
>>>> queue to split ingress packets into multiple segments to the mbufs
>>>> allocated from various memory pools according to the specified
>>>> lengths. The zero value of rx_split_num field provides the backward
>>>> compatibility and queue should be configured in a regular way (with
>>>> single/multiple mbufs of the same data buffer length allocated from
>>>> the single memory pool).
>>>
>>> From the above description it is not 100% clear how it will coexist
>>> with:
>>> - existing mb_pool argument of the rte_eth_rx_queue_setup()
>>
>> +1
> - supposed to be NULL if the array of lengths/pools is used
>
>>
>>> - DEV_RX_OFFLOAD_SCATTER
>>> - DEV_RX_OFFLOAD_HEADER_SPLIT
>>> How will application know that the feature is supported? Limitations?
>>
>> +1
> New flag DEV_RX_OFFLOAD_BUFFER_SPLIT is supposed to be introduced.
> The feature requires the DEV_RX_OFFLOAD_SCATTER is set.
> If DEV_RX_OFFLOAD_HEADER_SPLIT is set the error is returned.
>
>>
>>> Is it always split by specified/fixed length?
>>> What happens if header length is actually different?
>>
>> As far as I understand intention is to filter specific packets to a queue
>> first
>> and later do the split, so the header length will be fixed...
>
> Not exactly. The filtering should be handled by rte_flow engine.
> The intention is to provide the more flexible way to describe
> rx buffers. Currently it is the single pool with fixed size segments. No way
> to
> split the packet into multiple segments with specified lengths and in
> the specified pools. What if packet payload should be stored in the physical
> memory on other device (GPU/Storage)? What if caching is not desired for
> the payload (just forwarding application)? We could provide the special NC
> pool.
> What if packet should be split into the chunks with specific gaps?
> For Tx direction we have this opportunity to gather packet from various
> pools and any desired combinations , but Rx is much less flexible.
>
>>>
>>>> The new approach would allow splitting the ingress packets into
>>>> multiple parts pushed to the memory with different attributes.
>>>> For example, the packet headers can be pushed to the embedded data
>>>> buffers within mbufs and the application data into the external
>>>> buffers attached to mbufs allocated from the different memory pools.
>>>> The memory attributes for the split parts may differ either - for
>>>> example the application data may be pushed into the external memory
>>>> located on the dedicated physical device, say GPU or NVMe. This would
>>>> improve the DPDK receiving datapath flexibility preserving
>>>> compatibility with existing API.
If you don't know the packet types in advance, how can you use fixed sizes to
split a packet? Won't it be like having random parts of packet in each mempool..
>>>>
>>>> Signed-off-by: Viacheslav Ovsiienko <viachesl...@mellanox.com>
>>>> ---
>>>> doc/guides/rel_notes/deprecation.rst | 5 +++++
>>>> 1 file changed, 5 insertions(+)
>>>>
>>>> diff --git a/doc/guides/rel_notes/deprecation.rst
>>>> b/doc/guides/rel_notes/deprecation.rst
>>>> index ea4cfa7..cd700ae 100644
>>>> --- a/doc/guides/rel_notes/deprecation.rst
>>>> +++ b/doc/guides/rel_notes/deprecation.rst
>>>> @@ -99,6 +99,11 @@ Deprecation Notices
>>>> In 19.11 PMDs will still update the field even when the offload is not
>>>> enabled.
>>>>
>>>> +* ethdev: add new fields to ``rte_eth_rxconf`` to configure the
>>>> +receiving
>>>> + queues to split ingress packets into multiple segments according
>>>> +to the
>>>> + specified lengths into the buffers allocated from the specified
>>>> + memory pools. The backward compatibility to existing API is preserved.
>>>> +
>>>> * ethdev: ``rx_descriptor_done`` dev_ops and
>> ``rte_eth_rx_descriptor_done``
>>>> will be deprecated in 20.11 and will be removed in 21.11.
>>>> Existing ``rte_eth_rx_descriptor_status`` and
>>>> ``rte_eth_tx_descriptor_status``
>>>
>
