em performs worse than igb (latency wise) in 12?

[Kris von Mach]

On 4/6/2019 2:56 AM, Pete French wrote:
> Something odd going on there there - I am using 12-STABLE and I have 
> igb just fine, and it attaches to the same hardware that 11 did:

I ran apache bench, and I got a result of 100 requests/sec on 12-STABLE 
vs 16,000 requests/sec on 11-STABLE. So something is definitely wrong. 
Nothing changed other than going from 11 to 12.

ab on 12-STABLE:

ab -n 100 -c 10 http://ip/
This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking ip (be patient).....done


Server Software:        nginx
Server Hostname:        ip
Server Port:            80

Document Path:          /
Document Length:        16247 bytes

Concurrency Level:      10
Time taken for tests:   1.013 seconds
Complete requests:      100
Failed requests:        0
Total transferred:      1649900 bytes
HTML transferred:       1624700 bytes
Requests per second:    98.69 [#/sec] (mean)
Time per request:       101.331 [ms] (mean)
Time per request:       10.133 [ms] (mean, across all concurrent requests)
Transfer rate:          1590.07 [Kbytes/sec] received

Connection Times (ms)
               min  mean[+/-sd] median   max
Connect:        0    0   0.2      0       1
Processing:   100  101   0.5    101     102
Waiting:        0    0   0.1      0       1
Total:        100  101   0.6    101     102

Percentage of the requests served within a certain time (ms)
   50%    101
   66%    101
   75%    101
   80%    102
   90%    102
   95%    102
   98%    102
   99%    102
  100%    102 (longest request)

ab on 11-STABLE:

ab -n 100 -c 10 http://ip/
This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking ip (be patient).....done


Server Software:        nginx
Server Hostname:        ip
Server Port:            80

Document Path:          /
Document Length:        16247 bytes

Concurrency Level:      10
Time taken for tests:   0.006 seconds
Complete requests:      100
Failed requests:        0
Total transferred:      1651400 bytes
HTML transferred:       1624700 bytes
Requests per second:    16123.83 [#/sec] (mean)
Time per request:       0.620 [ms] (mean)
Time per request:       0.062 [ms] (mean, across all concurrent requests)
Transfer rate:          260028.27 [Kbytes/sec] received

Connection Times (ms)
               min  mean[+/-sd] median   max
Connect:        0    0   0.0      0       0
Processing:     0    0   0.1      0       1
Waiting:        0    0   0.0      0       1
Total:          0    1   0.0      1       1

Percentage of the requests served within a certain time (ms)
   50%      1
   66%      1
   75%      1
   80%      1
   90%      1
   95%      1
   98%      1
   99%      1
  100%      1 (longest request)