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Re: [lwip-users] Throughput benchmark question - nasty ~1.5 second pause

From: Dave Nadler
Subject: Re: [lwip-users] Throughput benchmark question - nasty ~1.5 second pauses
Date: Mon, 18 Mar 2019 16:41:41 -0400
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On 3/18/2019 9:15 AM, Sergio R. Caprile wrote:
The bug I mentioned is on the rx side, I see you are losing frames on
the tx side. There should be a frame between #4206 and #4207 that is
either lost inside your device or on its way to your PC.
The same pattern repeats where you mention, there is a missing frame
between #4315 and #4316.
I would hunt this instead.

To debug this, can you suggest a convenient place in LwIP to record the most
recent sequence# transmitted (or at least passed to the dubious driver)?

You don't seem to lose ACKs.
The retransmission triggers a bit late for what I like, but as Simon
points out, you have an unusual pattern. TCP always wants to wait before
sending, if you don't cram its buffer and just sit waiting for the
response, it will retransmit when it gets tired of waiting. But if you
want to keep sending, it will probably "insist" earlier.
As I mentioned before, try a known application. I would chase for those
missing frames on the output side, though.

You could also check your port is providing correct timing, but I guess
we can consider the FreeRTOS port as "standard" and "working" ?

FreeRTOS and timers appear solid; I've got a blinky task that keeps
blinking as expected during this nasty pause.

The ST-provided glue (driver, FreeRTOS-LwIP-driver binding code),
well that's a whole nuther terrible mess...

Thanks Sergio,
Best Regards, Dave

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Dave Nadler, USA East Coast voice (978) 263-0097, address@hidden, Skype 

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