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Date: Mon, 23 Jul 2018 10:37:57 -0700
From: Stephen Hemminger <stephen@networkplumber.org>
To: Morten =?UTF-8?B?QnLDuHJ1cA==?= <mb@smartsharesystems.com>
Cc: "Olivier Matz" <olivier.matz@6wind.com>, <dev@dpdk.org>
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Subject: Re: [dpdk-dev] rte_mbuf library likely()/unlikely()
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On Mon, 23 Jul 2018 15:53:42 +0200
Morten Br=C3=B8rup <mb@smartsharesystems.com> wrote:

> Hi Olivier,
>=20
> =20
>=20
> I noticed that __rte_pktmbuf_read() could do with an unlikely(), so I wen=
t through the entire library. Here are my suggested modifications.
>=20
> =20
>=20
> =20
>=20
> diff -bu rte_mbuf.c.orig rte_mbuf.c
>=20
> --- rte_mbuf.c.orig     2018-07-23 15:13:22.000000000 +0200
>=20
> +++ rte_mbuf.c  2018-07-23 15:32:53.000000000 +0200
>=20
> @@ -173,19 +173,19 @@
>=20
> {
>=20
>         unsigned int nb_segs, pkt_len;
>=20
> =20
>=20
> -       if (m =3D=3D NULL)
>=20
> +       if (unlikely(m =3D=3D NULL))
>=20
>                 rte_panic("mbuf is NULL\n");
>=20
> =20

Adding is unlikely is not necessary since rte_panic is marked with cold att=
ribute
which has the same effect.