High sysbench -- thread instead of low latency-CodePudding

Using sysbench test, found that the sending thread, less delay rather high, which may lead to the phenomenon, please?

Machine: DELL R730 20 c/256 g
Operating system: centos7
The database version: mysql8.0

Supplement:
1. The test data after preheating
2. Using the Unix works the same way socket send

- the number of threads to 5
# sysbench select_random_ranges. Lua - auto - inc=off - mysql - user=test - mysql - password='111' - mysql - host=127.0.0.1 - mysql - port=3306 - mysql db=db_test - db - ps - mode=disable - tables=100 - table_size=100000 - threads=5 - events=0 - time=30 - rand - type=special - report - interval=5 run
Sysbench 1.1.0 (using bundled LuaJIT 2.1.0 -beta3)

Running the test with the following options:
Number of threads: 5
The Report intermediate results every 5 second (s)
The Initializing the random number generator from the current time

The Initializing the worker threads...

Threads started!

[5] s THDS: 5 TPS: QPS: 18559.75 18559.75 (r/w/o: 0.00/18559.75/0.00) lat (ms, 95%) : err/s 0.32:0.00 reconn/s: 0.00
[s] 10 THDS: 5 TPS: QPS: 18378.06 18378.06 (r/w/o: 0.00/18378.06/0.00) lat (ms, 95%) : err/s 0.30:0.00 reconn/s: 0.00
[s] 15 THDS: 5 TPS: QPS: 17994.46 17994.66 (r/w/o: 0.00/17994.66/0.00) lat (ms, 95%) : err/s 0.35:0.00 reconn/s: 0.00
[s] 20 THDS: 5 TPS: QPS: 17905.29 17905.09 (r/w/o: 0.00/17905.09/0.00) lat (ms, 95%) : err/s 0.36:0.00 reconn/s: 0.00
[s] 25 THDS: 5 TPS: QPS: 18536.68 18536.68 (r/w/o: 0.00/18536.68/0.00) lat (ms, 95%) : err/s 0.31:0.00 reconn/s: 0.00
The SQL statistics:
The queries performed:
Read: 548087
Write: 0
Other: 0
Total: 548087
The transactions: 548087 (18267.22 per SEC.)
The queries: 548087 (18267.22 per SEC.)
Ignored errors: 0 (0.00 per SEC.)
Reconnects: 0 (0.00 per SEC.)

Throughput:
The events/s (eps) : 18267.2230
Time elapsed: 30.0038 s
The total number of events: 548087

Latency (ms) :
Min: 0.14
avg: 0.27
Max: 21.90
95th the percentile: 0.34
Sum: 149352.89

Threads fairness:
109617.4000/46844.87 events (avg/stddev) :
Execution time (avg/stddev) : 29.8706/0.04

- the number of threads to 1
# sysbench select_random_ranges. Lua - auto - inc=off - mysql - user=test - mysql - password='111' - mysql - host=127.0.0.1 - mysql - port=3306 - mysql db=db_test - db - ps - mode=disable - tables=100 - table_size=100000 - threads=1 - events=0 - time=30 - rand - type=special - report - interval=5 run
Sysbench 1.1.0 (using bundled LuaJIT 2.1.0 -beta3)

Running the test with the following options:
The Number of threads: 1
The Report intermediate results every 5 second (s)
The Initializing the random number generator from the current time

The Initializing the worker threads...

Threads started!

[5] s THDS: 1 TPS: QPS: 644.83 644.83 (r/w/o: 0.00/644.83/0.00) lat (ms, 95%) : err/s 1.96:0.00 reconn/s: 0.00
[s] 10 THDS: 1 TPS: QPS: 634.44 634.44 (r/w/o: 0.00/634.44/0.00) lat (ms, 95%) : err/s 1.96:0.00 reconn/s: 0.00
[s] 15 THDS: 1 TPS: QPS: 611.43 611.43 (r/w/o: 0.00/611.43/0.00) lat (ms, 95%) : err/s 2.07:0.00 reconn/s: 0.00
[s] 20 THDS: 1 TPS: QPS: 611.72 611.72 (r/w/o: 0.00/611.72/0.00) lat (ms, 95%) : err/s 2.03:0.00 reconn/s: 0.00
[s] 25 THDS: 1 TPS: QPS: 600.83 600.83 (r/w/o: 0.00/600.83/0.00) lat (ms, 95%) : err/s 2.07:0.00 reconn/s: 0.00
The SQL statistics:
The queries performed:
Read: 18548
Write: 0
Other: 0
Total: 18548
The transactions: 18548 (618.20 per SEC.)
The queries: 18548 (618.20 per SEC.)
Ignored errors: 0 (0.00 per SEC.)
Reconnects: 0 (0.00 per SEC.)

Throughput:
The events/s (eps) : 618.1982
Time elapsed: 30.0033 s
The total number of events: 18548

Latency (ms) :
Min: 0.45
avg: 1.61
Max: 15.20
95th the percentile: 2.03
Sum: 29942.56

Threads fairness:
18548.0000/0.00 events (avg/stddev) :
Execution time (avg/stddev) : 29.9426/0.00