[PATCH] mbuf: optimize segment prefree

[Morten Brørup]

> From: Wathsala Vithanage [mailto:wathsala.vithanage at arm.com]
> Sent: Monday, 6 October 2025 19.46
> 
> On 8/27/25 18:17, Stephen Hemminger wrote:
> > On Wed, 27 Aug 2025 21:35:34 +0000
> > Morten Brørup <mb at smartsharesystems.com> wrote:
> >
> >>
> >> +/* GCC only optimizes single-bit MSB tests this way, so do it by
> hand with multi-bit. */
> >> +#if defined(RTE_TOOLCHAIN_GCC) && defined(RTE_ARCH_X86)
> >> +#undef RTE_MBUF_DIRECT
> >> +#define RTE_MBUF_DIRECT(mb) \
> >> +	(!(((const uint8_t *)(mb))[offsetof(struct rte_mbuf, ol_flags) +
> 7] & \
> >> +	(uint8_t)((RTE_MBUF_F_INDIRECT | RTE_MBUF_F_EXTERNAL) >> 56)))
> >> +#endif
> > Complex enough expression that I would prefer this be an inline
> function
> > with some more temporary variables and more comments.
> > Like the magic 7 for mask??
> 
> +1

So, instead of overriding the macro definition in the GCC exception case, you prefer something like:
#if defined(RTE_TOOLCHAIN_GCC) && defined(RTE_ARCH_X86)
static __rte_always_inline
RTE_MBUF_DIRECT(const struct rte_mbuf * const mb)
{...}
#else
#define RTE_MBUF_DIRECT(mb) \
	(!((mb)->ol_flags & (RTE_MBUF_F_INDIRECT | RTE_MBUF_F_EXTERNAL)))
#endif

which would give us a function with a macro-like (upper case) name.

How about I just add a more detailed description to this macro?
After all, formally, it's an exception to the simple default macro.