linux-kernel - Re: [PATCH v2 3/6] net: ocelot: pre-compute injection frame header content

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Date:   Mon, 15 Nov 2021 15:06:20 +0100
From:   Clément Léger <clement.leger@...tlin.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Vladimir Oltean <vladimir.oltean@....com>,
        "David S. Miller" <davem@...emloft.net>,
        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>
Subject: Re: [PATCH v2 3/6] net: ocelot: pre-compute injection frame header
 content

Le Mon, 15 Nov 2021 06:08:00 -0800,
Jakub Kicinski <kuba@...nel.org> a écrit :

> On Mon, 15 Nov 2021 11:13:44 +0100 Clément Léger 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

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