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From: Ferruh Yigit <ferruh.yigit@intel.com>
To: Slava Ovsiienko <viacheslavo@mellanox.com>,
	Andrew Rybchenko <arybchenko@solarflare.com>,
	"dev@dpdk.org" <dev@dpdk.org>
Cc: Matan Azrad <matan@mellanox.com>,
	Raslan Darawsheh <rasland@mellanox.com>,
	Thomas Monjalon <thomas@monjalon.net>,
	"jerinjacobk@gmail.com" <jerinjacobk@gmail.com>,
	"stephen@networkplumber.org" <stephen@networkplumber.org>,
	"ajit.khaparde@broadcom.com" <ajit.khaparde@broadcom.com>,
	"maxime.coquelin@redhat.com" <maxime.coquelin@redhat.com>,
	"olivier.matz@6wind.com" <olivier.matz@6wind.com>,
	"david.marchand@redhat.com" <david.marchand@redhat.com>
Subject: Re: [dpdk-dev] [PATCH] doc: announce changes to ethdev rxconf structure
Date: Thu, 6 Aug 2020 17:37:27 +0100
Message-ID: <1e555836-cd8d-9b06-f348-f1a0e2d77dbb@intel.com> (raw)
In-Reply-To: <AM4PR05MB3265283827B70489DB5D2D05D2480@AM4PR05MB3265.eurprd05.prod.outlook.com>

On 8/6/2020 5:29 PM, Slava Ovsiienko wrote:
>> -----Original Message-----
>> From: Ferruh Yigit <ferruh.yigit@intel.com>
>> Sent: Thursday, August 6, 2020 19:16
>> To: Andrew Rybchenko <arybchenko@solarflare.com>; Slava Ovsiienko
>> <viacheslavo@mellanox.com>; dev@dpdk.org
>> Cc: Matan Azrad <matan@mellanox.com>; Raslan Darawsheh
>> <rasland@mellanox.com>; Thomas Monjalon <thomas@monjalon.net>;
>> jerinjacobk@gmail.com; stephen@networkplumber.org;
>> ajit.khaparde@broadcom.com; maxime.coquelin@redhat.com;
>> olivier.matz@6wind.com; david.marchand@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 <viacheslavo@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``
>>>
> 


  reply	other threads:[~2020-08-06 16:37 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-03 10:58 Viacheslav Ovsiienko
2020-08-03 11:56 ` Jerin Jacob
2020-08-03 13:06   ` Slava Ovsiienko
2020-08-04 13:32     ` Jerin Jacob
2020-08-05  6:35       ` Slava Ovsiienko
2020-08-06 15:58       ` Ferruh Yigit
2020-08-06 16:25         ` Stephen Hemminger
2020-08-06 16:41           ` Jerin Jacob
2020-08-06 17:03           ` Slava Ovsiienko
2020-08-06 18:10             ` Stephen Hemminger
2020-08-07 11:23               ` Slava Ovsiienko
2020-08-03 14:31 ` [dpdk-dev] ***Spam*** " Andrew Rybchenko
2020-08-06 16:15   ` [dpdk-dev] " Ferruh Yigit
2020-08-06 16:29     ` Slava Ovsiienko
2020-08-06 16:37       ` Ferruh Yigit [this message]
2020-08-06 16:39         ` Slava Ovsiienko
2020-08-06 16:43           ` Ferruh Yigit
2020-08-06 16:48             ` Slava Ovsiienko
2020-08-05  8:49 ` [dpdk-dev] [PATCH v2] " Viacheslav Ovsiienko
2020-08-05 11:14   ` Andrew Rybchenko
2020-08-06 12:39     ` Thomas Monjalon
2020-08-06 21:42       ` Thomas Monjalon
2020-08-06 16:31   ` Ferruh Yigit
2020-08-06 17:00     ` Slava Ovsiienko
2020-08-06 16:55   ` [dpdk-dev] [PATCH v2] doc: fix the release notes for Mellanox PMD Viacheslav Ovsiienko
2020-08-06 17:12     ` Asaf Penso
2020-08-06 22:37       ` Thomas Monjalon
2020-08-03 15:18 [dpdk-dev] [PATCH] doc: announce changes to ethdev rxconf structure Slava Ovsiienko
2020-08-03 15:31 ` Andrew Rybchenko
2020-08-03 16:51   ` Slava Ovsiienko
2020-08-30 12:58     ` Andrew Rybchenko
2020-08-30 18:26       ` Stephen Hemminger
2020-08-31  6:35         ` Andrew Rybchenko
2020-08-31 16:59           ` Stephen Hemminger

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