From:   Vladimir Oltean <vladimir.oltean@nxp.com>
To:     =?iso-8859-1?Q?Cl=E9ment_L=E9ger?= <clement.leger@bootlin.com>
CC:     Jakub Kicinski <kuba@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Rob Herring <robh+dt@kernel.org>,
        Claudiu Manoil <claudiu.manoil@nxp.com>,
        Alexandre Belloni <alexandre.belloni@bootlin.com>,
        "UNGLinuxDriver@microchip.com" <UNGLinuxDriver@microchip.com>,
        Andrew Lunn <andrew@lunn.ch>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH v2 3/6] net: ocelot: pre-compute injection frame header
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Thread-Topic: [PATCH v2 3/6] net: ocelot: pre-compute injection frame header
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Thread-Index: AQHX0JQMizPbr20xM0ur1htXAvgjtKvxviqAgAAVJICAEp56AIAAQXQA////iQCAAAbqgA==
Date:   Mon, 15 Nov 2021 14:31:06 +0000
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On Mon, Nov 15, 2021 at 03:06:20PM +0100, Cl=E9ment L=E9ger wrote:
> Le Mon, 15 Nov 2021 06:08:00 -0800,
> Jakub Kicinski <kuba@kernel.org> a =E9crit :
>
> > On Mon, 15 Nov 2021 11:13:44 +0100 Cl=E9ment L=E9ger wrote:
> > > Test on standard packets with UDP (iperf3 -t 100 -l 1460 -u -b 0 -c *=
)
> > > - With pre-computed header: UDP TX: 	33Mbit/s
> > > - Without UDP TX: 			31Mbit/s
> > > -> 6.5% improvement
> > >
> > > Test on small packets with UDP (iperf3 -t 100 -l 700 -u -b 0 -c *)
> > > - With pre-computed header: UDP TX: 	15.8Mbit/s
> > > - Without UDP TX: 			16.4Mbit/s
> > > -> 4.3% improvement
> >
> > Something's wrong with these numbers or I'm missing context.
> > You say improvement in both cases yet in the latter case the
> > new number is lower?
>
> You are right Jakub, I swapped the last two results,
>
> Test on small packets with UDP (iperf3 -t 100 -l 700 -u -b 0 -c *)
>  - With pre-computed header: UDP TX: 	16.4Mbit/s
>  - Without UDP TX: 			15.8Mbit/s
>  -> 4.3% improvement

Even in reverse, something still seems wrong with the numbers.
My DSPI controller can transfer at a higher data rate than that.
Where is the rest of the time spent? Computing checksums?=