linux-kernel - Re: [PATCH net-next v3 3/4] net: ocelot: pre-compute injection frame header content

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Date:   Fri, 26 Nov 2021 18:57:27 +0100
From:   Clément Léger <clement.leger@...tlin.com>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        Andrew Lunn <andrew@...n.ch>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Denis Kirjanov <dkirjanov@...e.de>,
        Julian Wiedmann <jwi@...ux.ibm.com>
Subject: Re: [PATCH net-next v3 3/4] net: ocelot: pre-compute injection
 frame header content

Le Fri, 26 Nov 2021 17:54:55 +0000,
Vladimir Oltean <vladimir.oltean@....com> a écrit :

> On Fri, Nov 26, 2021 at 06:27:38PM +0100, Clément Léger wrote:
> > IFH preparation can take quite some time on slow processors (up to 5% in
> > a iperf3 test for instance). In order to reduce the cost of this
> > preparation, pre-compute IFH since most of the parameters are fixed per
> > port. Only rew_op and vlan tag will be set when sending if different
> > than 0. This allows to remove entirely the calls to packing() with basic
> > usage. In the same time, export this function that will be used by FDMA.
> > 
> > Signed-off-by: Clément Léger <clement.leger@...tlin.com>
> > ---  
> 
> If you would move this injection frame header template into struct
> ocelot_port_private instead of struct ocelot_port, I would not have
> anything against it. Because struct ocelot_port is common with DSA,
> whereas struct ocelot_port_private isn't.
> 
> Also, as things stand, all switch drivers call ocelot_init_port, but not
> all supported switches have the same IFH format. See seville_xmit() ->
> seville_ifh_set_dest(). So even though DSA does not use this for
> anything, it wouldn't even contain valid information even if it wanted
> to. So maybe you can move this initialization to some place isolated to
> vsc7514.

Acked, this makes sense, I will do this.

-- 
Clément Léger,
Embedded Linux and Kernel engineer at Bootlin
https://bootlin.com