[dpdk-dev] [PATCH v2 2/7] ethdev: add mbuf RSS update as an offload

[Stephen Hemminger]

On Thu, 22 Aug 2019 02:17:50 +0530
<pbhagavatula at marvell.com> wrote:

> From: Pavan Nikhilesh <pbhagavatula at marvell.com>
> 
> Add new Rx offload flag `DEV_RX_OFFLOAD_RSS_HASH` which can be used to
> enable/disable PMDs write to `rte_mbuf::hash::rss`.
> PMDs notify the validity of `rte_mbuf::hash:rss` to the applcation
> by enabling `PKT_RX_RSS_HASH ` flag in `rte_mbuf::ol_flags`.
> 
> Signed-off-by: Pavan Nikhilesh <pbhagavatula at marvell.com>
> Reviewed-by: Andrew Rybchenko <arybchenko at solarflare.com>

Is this really a good idea?
Every bit of hardware that works on Windows with RSS is required to
supply the hash (for software steering).  So if adding an additional
capability, just adds another bit of complexity, code coverage, and one
more thing that won't be tested by everyone.

If hardware has it why not set it? Adding a branch is more expensive than
an unused assignment.