Use minions to learn epoll
lazarus / 38-Networking and Web Programming

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Tz · 2019-08-04 02:49

Im looking for epoll and start searching this forum and found this
topic https://forum.lazarus.freepascal.org/index.php/topic,9352.0

but it was so long ago, and feel a progress way too little, thanks for
hint from zamronypj

I would make epoll a new start, even just a bit, and here epoll with
minions.

Hope someone can make start on iocp too.

What I learn

  1. Thundering herd problem, to avoid that, I simply use single
thread (main thread)
     so no listener sharing. For scale just increase SOMAXCONN.
     Anyone would like to try Acceptor Thread as number of core cpu?

  2. A listener use level trigger, and for acceptor use edge trigger,
     and by these all message should be full in one transmission,
     best for short message, but dont know for large bytes such upload
file.
     just I dont know how to do it.

  3. A processing of ready list, after epoll wait, we have to process
much much faster.
     My first attempt use single thread it just block.
     For accept should be fast just set option and register to epoll
(epoll.add)
     And for EPOOLIN I use to spawn a minion thread,
     I think this is good for concurency, and can process
asynchronously.
     and dont forget to  FreeOnTerminate := true;
     Also we can try to create a thread pool, to reduce of thread cost
creation?
     any clue ?

  4. Some socket option still need tuning, theres note in zsockopt.pas
     and refer to these topic
https://forum.lazarus.freepascal.org/index.php/topic,44788.0
     for benchmarking.

     And this my current benchmark.


$ ab -n 9000 -c 9000 http://localhost:8000/
This is ApacheBench, Version 2.3 <$Revision: 1807734 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd,
http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking localhost (be patient)
Completed 900 requests
Completed 1800 requests
Completed 2700 requests
Completed 3600 requests
Completed 4500 requests
Completed 5400 requests
Completed 6300 requests
Completed 7200 requests
Completed 8100 requests
Completed 9000 requests
Finished 9000 requests


Server Software:
Server Hostname:        localhost
Server Port:            8000

Document Path:          /
Document Length:        37 bytes

Concurrency Level:      9000
Time taken for tests:   0.885 seconds
Complete requests:      9000
Failed requests:        0
Total transferred:      1386000 bytes
HTML transferred:       333000 bytes
Requests per second:    10170.11 [#/sec] (mean)
Time per request:       884.946 [ms] (mean)
Time per request:       0.098 [ms] (mean, across all concurrent
requests)
Transfer rate:          1529.49 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:      142  216  42.0    218     288
Processing:   155  257 100.2    229     458
Waiting:      122  251 106.9    229     458
Total:        405  473  60.3    447     601

Percentage of the requests served within a certain time (ms)
  50%    447
  66%    494
  75%    522
  80%    538
  90%    571
  95%    586
  98%    595
  99%    598
 100%    601 (longest request)



the code is not good enough, but I hope we all can make another start.

Lets make Pascal great again

attach source code.