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Subject: RE: [RFC PATCH 27/27] net/intel: remove index for tracking end of
 packet
Date: Sat, 20 Dec 2025 10:05:45 +0100
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Thread-Topic: [RFC PATCH 27/27] net/intel: remove index for tracking end of
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From: =?iso-8859-1?Q?Morten_Br=F8rup?= <mb@smartsharesystems.com>
To: "Bruce Richardson" <bruce.richardson@intel.com>,
	<dev@dpdk.org>
Cc: "Vladimir Medvedkin" <vladimir.medvedkin@intel.com>,
 "Anatoly Burakov" <anatoly.burakov@intel.com>,
 "Jingjing Wu" <jingjing.wu@intel.com>,
 "Praveen Shetty" <praveen.shetty@intel.com>
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> From: Bruce Richardson [mailto:bruce.richardson@intel.com]
> Sent: Friday, 19 December 2025 18.26
>=20
> The last_id value in each tx_sw_queue entry was no longer used in the
> datapath, remove it and its initialization. For the function releasing
> packets back, rather than relying on "last_id" to identify end of
> packet, instead check for the next pointer being NULL.
>=20
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
> ---

[...]

> @@ -2523,14 +2523,13 @@ i40e_tx_done_cleanup_full(struct ci_tx_queue
> *txq,
>  			pkt_cnt < free_cnt &&
>  			tx_id !=3D tx_last; i++) {
>  			if (swr_ring[tx_id].mbuf !=3D NULL) {
> -				rte_pktmbuf_free_seg(swr_ring[tx_id].mbuf);
> -				swr_ring[tx_id].mbuf =3D NULL;
> -
>  				/*
>  				 * last segment in the packet,
>  				 * increment packet count
>  				 */
> -				pkt_cnt +=3D (swr_ring[tx_id].last_id =3D=3D tx_id);
> +				pkt_cnt +=3D (swr_ring[tx_id].mbuf->next =3D=3D NULL)
> ? 1 : 0;

Note to reviewers:
Dereferencing the mbuf (instead of checking last_id) does not add a =
potential cache miss, because rte_pktmbuf_free_seg() dereferences it =
anyway.

> +				rte_pktmbuf_free_seg(swr_ring[tx_id].mbuf);
> +				swr_ring[tx_id].mbuf =3D NULL;
>  			}
>=20
>  			tx_id =3D swr_ring[tx_id].next_id;