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Re: [lwip-users] Improving UDP responses.


From: Bill Auerbach
Subject: Re: [lwip-users] Improving UDP responses.
Date: Wed, 13 Oct 2021 15:49:00 +0000

Hi,

I know I'm late to the party but UDP throughput problems have to be at the 
driver level.  We produce an lwIP-based camera (752x480) on a slow 100Mhz CPLD 
softcore and with UDP for image transfers to the PC it can send over 60 images 
a second continuously.  This includes our own method for reliable transfers for 
dropped packets (which never happen on a private subnet unless 2 or more 
cameras are sending images at the same time). We don't need this speed 5 - 10 
per second is all we need, but it was a good test to run as fast as it will go 
and this is what we can achieve.  To be fair, this includes the image packet 
checksums being done in hardware, but that wasn't a big bottleneck before we 
did that.

Bill

-----Original Message-----
From: lwip-users <lwip-users-bounces+bauerbach=arrayonline.com@nongnu.org> On 
Behalf Of goldsimon@gmx.de
Sent: Tuesday, September 21, 2021 1:50 PM
To: Mailing list for lwIP users <lwip-users@nongnu.org>
Subject: Re: [lwip-users] Improving UDP responses.

Am 21.09.2021 um 14:59 schrieb Luciano Moretti:
> I've got an STM32F7 (SPL, not HAL) based project using LwIP RAW. We've 
> got it working fairly well, but it seems to handle 6 UDP packets very 
> quickly and then start dropping packets. I thought it was because of 
> the MEMP_NUM_UDP_PCB which was defined as 6, but increasing it to 12 
> has had no effect.
>
> Can you make any other recommendations as to how to increase our throughput?

I'm not aware of anything in lwIP limiting you here. It could be any memory 
shortage (debug this using lwip_stats) or it could be a driver issue somehow 
limiting the number of frames you can pull off your netif.

The STM drivers were somewhat buggy when I worked with them. Now some years 
have passed since then, but I don't know if they have been fixed by now.

Regards,
Simon

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