[PATCH v2] doc, eal, devtools: discourage new __rte_always_inline

[Morten Brørup]

> From: Stephen Hemminger [mailto:stephen at networkplumber.org]
> Sent: Monday, 1 June 2026 19.21
> 
> Modern compilers at -O2 make good inlining decisions for small
> static inline functions; forced inlining via __rte_always_inline
> should be reserved for cases where it is required for correctness
> or for documented measured performance reasons.
> 
> Document the policy in the coding style guide and add a
> checkpatches.sh entry that flags when new uses of the attribute
> are introduced. Checkpatches is not an absolute blocker to
> acceptance, only an indicator that more review is needed.
> 
> Add additional comments about use of __rte_always_inline,
> __rte_noinline, __rte_hot, and __rte_cold to the rte_common.h
> to aid developers.
> 
> Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
> ---

Reviewed-by: Morten Brørup <mb at smartsharesystems.com>