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Date: Fri, 8 Dec 2023 15:44:46 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Christoph Paasch <cpaasch@apple.com>
Cc: netdev <netdev@vger.kernel.org>, Roopa Prabhu <roopa@nvidia.com>, Craig
 Taylor <cmtaylor@apple.com>
Subject: Re: mpls_xmit() calls skb_orphan()
Message-ID: <20231208154446.0feee63f@kernel.org>
In-Reply-To: <7915A22A-F1ED-4A5D-AC2A-25D0C05ECAA0@apple.com>
References: <9F1B6AC3-509E-4C64-97A4-47247F25913A@apple.com>
	<7915A22A-F1ED-4A5D-AC2A-25D0C05ECAA0@apple.com>
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Updating Roopa's email.

On Fri, 08 Dec 2023 13:15:04 -0800 Christoph Paasch wrote:
> > On Dec 8, 2023, at 1:06=E2=80=AFPM, Christoph Paasch <cpaasch@apple.com=
> wrote:
> >=20
> > Hello,
> >=20
> > we observed an issue when running a TCP-connection with BBR on top of a=
n MPLS-tunnel in that we saw a lot of CPU-time spent coming from tcp_pace_k=
ick(), although sch_fq was configured on this host.
> >=20
> > The reason for this seems to be because mpls_xmit() calls skb_orphan(),=
 thus settings skb->sk to NULL, preventing the qdisc to set sk_pacing_statu=
s (which would allow to avoid the call to tcp_pace_kick()).
> >=20
> > The question is: Why is this call to skb_orphan in mpls_xmit necessary ?
> >=20
> >=20
> > Thanks,
> > Christoph =20
>=20
> Resend in plain-text. Sorry about that!