Re: [PATCH v2 1/5] ethdev: support setting and querying RSS algorithm

[Thomas Monjalon <thomas@monjalon.net>]

04/09/2023 09:10, Jie Hai:
> On 2023/8/30 19:46, Thomas Monjalon wrote:
> > 26/08/2023 09:46, Jie Hai:
 >> + * The *func* field of the *rss_conf* structure indicates the hash algorithm
> >> + * applied by the RSS hashing. Passing RTE_ETH_HASH_FUNCTION_DEFAULT allows
> >> + * the PMD to use its best-effort algorithm rather than a specific one.
> >>    */
> > 
> > I don't like commenting a field on top of the structure.
> > By the way, the first sentence does not look helpful.
> > RTE_ETH_HASH_FUNCTION_DEFAULT may be explained in the enum.
> > 
> Other fields  above the structure 'rte_eth_rss_conf' have comments.
> If the new fields 'func' do not have comments, it may be misleading.
> Unless all the comments above are removed. I'm not sure whether to
> delete them or not.

You should explain RTE_ETH_HASH_FUNCTION_DEFAULT in its enum.
The rest of the explanation can be on the struct field.
I'm OK to have another patch moving old explanations from the struct
to the fields.

> >>   struct rte_eth_rss_conf {
> >>   	uint8_t *rss_key;    /**< If not NULL, 40-byte hash key. */
> >>   	uint8_t rss_key_len; /**< hash key length in bytes. */
> >>   	uint64_t rss_hf;     /**< Hash functions to apply - see below. */
> >> +	enum rte_eth_hash_function func;	/**< Hash algorithm to apply. */
> > 
> > You can drop "to apply" words.
> Fixed in V3.
> > 
> > How the algorithms support combinations in rss_hf?
> > 
> The rss_hf defines the input of the RSS hash algorithms.
> For example, rss_hf = RTE_ETH_RSS_NONFRAG_IPV4_TCP | RTE_ETH_RSS_IPV4, 
> these two kinds of packets can be dispatched to different queues 
> according to their tuple field value.
> For ipv4-tcp packets, src-ip, dst-ip, src-port, dst-port are used as 
> parameters of RSS hash algorithms to compute hash value.
> For ipv4 packets src-ip, dst-ip are used.
> 
> If rss_hf = RTE_ETH_RSS_NONFRAG_IPV4_TCP | RTE_ETH_RSS_L4_SRC_ONLY, for
> ipv4-tcp packets, src-port is used as parameters of RSS hash algorithms 
> to compute hash value.

I know what is rss_hf.
My question is about the algorithms.
Do they all support any combination in rss_hf?