netdev - RE: [PATCH net-next 00/12] mlxsw: Preparations for XDP support

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Message-ID:
 <BL1PR12MB5922564282DA2C2C5CA671C1CBF42@BL1PR12MB5922.namprd12.prod.outlook.com>
Date: Tue, 4 Feb 2025 17:26:43 +0000
From: Amit Cohen <amcohen@...dia.com>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
CC: Petr Machata <petrm@...dia.com>, "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo
 Abeni <pabeni@...hat.com>, Andrew Lunn <andrew+netdev@...n.ch>, Network
 Development <netdev@...r.kernel.org>, Ido Schimmel <idosch@...dia.com>,
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend
	<john.fastabend@...il.com>, bpf <bpf@...r.kernel.org>, mlxsw
	<mlxsw@...dia.com>
Subject: RE: [PATCH net-next 00/12] mlxsw: Preparations for XDP support



> -----Original Message-----
> From: Alexei Starovoitov <alexei.starovoitov@...il.com>
> Sent: Tuesday, 4 February 2025 18:02
> To: Amit Cohen <amcohen@...dia.com>
> Cc: Petr Machata <petrm@...dia.com>; David S. Miller <davem@...emloft.net>; Eric Dumazet <edumazet@...gle.com>; Jakub Kicinski
> <kuba@...nel.org>; Paolo Abeni <pabeni@...hat.com>; Andrew Lunn <andrew+netdev@...n.ch>; Network Development
> <netdev@...r.kernel.org>; Ido Schimmel <idosch@...dia.com>; Alexei Starovoitov <ast@...nel.org>; Daniel Borkmann
> <daniel@...earbox.net>; Jesper Dangaard Brouer <hawk@...nel.org>; John Fastabend <john.fastabend@...il.com>; bpf
> <bpf@...r.kernel.org>; mlxsw <mlxsw@...dia.com>
> Subject: Re: [PATCH net-next 00/12] mlxsw: Preparations for XDP support
> 
> On Tue, Feb 4, 2025 at 3:59 PM Amit Cohen <amcohen@...dia.com> wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: Alexei Starovoitov <alexei.starovoitov@...il.com>
> > > Sent: Tuesday, 4 February 2025 17:56
> > > To: Petr Machata <petrm@...dia.com>
> > > Cc: David S. Miller <davem@...emloft.net>; Eric Dumazet <edumazet@...gle.com>; Jakub Kicinski <kuba@...nel.org>; Paolo Abeni
> > > <pabeni@...hat.com>; Andrew Lunn <andrew+netdev@...n.ch>; Network Development <netdev@...r.kernel.org>; Amit Cohen
> > > <amcohen@...dia.com>; Ido Schimmel <idosch@...dia.com>; Alexei Starovoitov <ast@...nel.org>; Daniel Borkmann
> > > <daniel@...earbox.net>; Jesper Dangaard Brouer <hawk@...nel.org>; John Fastabend <john.fastabend@...il.com>; bpf
> > > <bpf@...r.kernel.org>; mlxsw <mlxsw@...dia.com>
> > > Subject: Re: [PATCH net-next 00/12] mlxsw: Preparations for XDP support
> > >
> > > On Tue, Feb 4, 2025 at 11:06 AM Petr Machata <petrm@...dia.com> wrote:
> > > >
> > > > Amit Cohen writes:
> > > >
> > > > A future patch set will add support for XDP in mlxsw driver. This set adds
> > > > some preparations.
> > >
> > > Why?
> > > What is the goal here?
> > > My understanding is that mlxsw is a hw switch and skb-s are used to
> > > implement tap functionality for few listeners.
> > > The volume of such packets is supposed to be small.
> > > Even if XDP is added there is a huge mismatch in packet rates.
> > > Hence the question. Why bother?
> >
> > You're right, most of packets should be handled by HW, XDP is mainly useful for telemetry.
> 
> Why skb path is not enough?

We get better packet rates using XDP, this can be useful to redirect packets to a server for analysis for example.