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Subject: RE: mbuf init questions
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Date: Tue, 5 Dec 2023 11:10:21 +0100
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Thread-Topic: mbuf init questions
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From: =?iso-8859-1?Q?Morten_Br=F8rup?= <mb@smartsharesystems.com>
To: "Bruce Richardson" <bruce.richardson@intel.com>
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> From: Bruce Richardson [mailto:bruce.richardson@intel.com]
> Sent: Tuesday, 5 December 2023 10.56
>=20
> On Tue, Dec 05, 2023 at 10:07:56AM +0100, Morten Br=F8rup wrote:
> > Why is m->nb_segs initialized in rte_pktmbuf_prefree_seg()?
> >
> > It's part of the m->rearm_data, and will be initialized on RX
> descriptor rearm anyway.
> >
> Presumably this is to have a sane default for apps that allocate
> buffers
> directly using mempool_get functions.

Ahh, yes... the great bypassing of the mbuf APIs!

>=20
> Overall, we probably need to document clearly for mbufs allocated =
using
> mempool apis rather than mbuf_alloc what fields are valid and what =
need
> to
> be initialized.

Good point. Since it has become customary - and generally accepted =
practice - to bypass the mbuf APIs and use the mempool APIs directly, we =
should document how to use the mempool APIs in an mbuf API context.

Spaghetti code, but everyone loves the performance benefits by doing it. =
Including myself. ;-)