[RFC] mbuf: performance optimization

[Morten Brørup]

> From: Stephen Hemminger [mailto:stephen at networkplumber.org]
> Sent: Sunday, 21 January 2024 18.08
> 
> On Sun, 21 Jan 2024 06:32:42 +0100
> Morten Brørup <mb at smartsharesystems.com> wrote:
> 
> > I suppose that reducing mbuf->nb_segs from 16 to 8 bit is realistic,
> considering that a maximum size IP packet (64 KB) is unlikely to use
> more than 64 plus some segments. Does anyone know of any use case with
> more than 255 segments in an mbuf?
> 
> There is the case of Linux internally using super large IPv6 (and now
> IPv4) frames.
> See RFC 2675 IPv6 jumbograms
> 
> https://netdevconf.info/0x15/slides/35/BIG%20TCP.pdf

Just took at brief look at it... I suppose something similar could grow into DPDK, so we are probably better prepared by leaving nb_segs at 16 bit.

Then the proposed optimization falls to the ground. :-(

Thanks for valuable feedback, Stephen. :-)