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

On Mon, Nov 15, 2021 at 03:06:20PM +0100, Clément Léger wrote:

Le Mon, 15 Nov 2021 06:08:00 -0800,
Jakub Kicinski [off-list ref] a écrit :

quoted

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

quoted

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?