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From: Konstantin Ananyev <konstantin.ananyev@huawei.com>
To: Stephen Hemminger <stephen@networkplumber.org>, "dev@dpdk.org"
 <dev@dpdk.org>
Subject: RE: unnecessary rx callbacks when zero packets
Thread-Topic: unnecessary rx callbacks when zero packets
Thread-Index: AQHaQZA1SvyjeiZtCEmhNpNS5aEiy7DQCQxg
Date: Mon, 8 Jan 2024 15:20:58 +0000
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rx callbacks when zero packets
>=20
> I noticed while looking at packet capture that currently the receive call=
backs
> get called even if there are no packets. This seems unnecessary since if
> nb_rx is zero, then there are no packets to look at.  My one concern is t=
hat
> an application could be using callbacks as some form of scheduling mechan=
ism
> which would be broken.

As I remember, original idea was to allow callbacks to inject new packets i=
f needed.

>=20
> The change would be:
>=20
>=20
> diff --git a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h
> index 21e3a21903ec..f64bf977c46e 100644
> --- a/lib/ethdev/rte_ethdev.h
> +++ b/lib/ethdev/rte_ethdev.h
> @@ -6077,7 +6077,7 @@ rte_eth_rx_burst(uint16_t port_id, uint16_t queue_i=
d,
>         nb_rx =3D p->rx_pkt_burst(qd, rx_pkts, nb_pkts);
>=20
>  #ifdef RTE_ETHDEV_RXTX_CALLBACKS
> -       {
> +       if (nb_rx > 0) {
>                 void *cb;
>=20
>                 /* rte_memory_order_release memory order was used when th=
e