What is the nature of server latency on the W5100?

Question

Arduino

Faced an inexplicable delay in web server responses on the W5100. The browser request is accepted and hangs for 3 - 9 seconds, then it is successfully processed and a response is issued.
Analysis of the work leads to the fact that the problem is in the Arduino Ethernet library.
The problem is observed in the flow of requests, single ones are processed absolutely normally.
I solved the problem and here is a detailed article about this https://geektimes.ru/post/259898/

Answer 1

Faced the same problem.
W5100 on one connection works well, but on several simultaneous connections it takes a long time to respond.
D:\OpenServer\modules\http\Apache-2.2.24\bin>ab.exe -n10 192.168.1.99/echo
Percentage of the requests served within a certain time (ms)
50% 18
66% 18
75% 18
80% 18
90% 18
95% 18
98% 18
99% 18
100% 18 (longest request)
------------
D:\OpenServer\modules\http\Apache-2.2.24\bin>ab .exe -n10 -c2 192.168.1.99/echo
Percentage of the requests served within a certain time (ms)
50% 18
66% 18
75% 143
80% 3000
90% 3028 99% 3028
95% 3028
98% 3028
100% 3028 (longest request)
------------
D:\OpenServer\modules\http\Apache-2.2.24\bin>ab.exe -n10 -c4 192.168.1.99/echo
Percentage of the requests served within a certain time (ms)
50% 6010
66% 6010
75% 8996
80% 9010
90% 12005
95% 12005
98% 12005
99% 12005
100% 12005 (longest request)

Answer 2

GT literally just had a pretty lengthy post on this subject. It's about the library bug you're writing about here. Even the corrected library code is posted there.
I will warn you: I did not check it myself, the association just worked. I suggest you figure it out and evaluate whether it works in your case. It would be great if you post your results here.