[root@bjhtxx var]# mongos --version
mongos version v3.6.1
git version: 025d4f4fe61efd1fb6f0005be20cb45a004093d1
OpenSSL version: OpenSSL 1.0.1e-fips 11 Feb 2013
allocator: tcmalloc
modules: none
build environment:
distmod: rhel62
distarch: x86_64
target_arch: x86_64

top shows as following:
top - 06:12:58 up 652 days, 16:14, 0 users, load average: 0.60, 0.39, 0.26
Tasks: 714 total, 1 running, 712 sleeping, 0 stopped, 1 zombie
Cpu(s): 2.5%us, 6.1%sy, 0.0%ni, 90.7%id, 0.0%wa, 0.0%hi, 0.6%si, 0.0%st
Mem: 131819804k total, 126707228k used, 5112576k free, 190928k buffers
Swap: 16777724k total, 0k used, 16777724k free, 61473624k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3249 root 20 0 2377m 423m 5744 S 323.2 0.3 270937:13 mongos
5900 root 20 0 2341m 316m 5732 S 62.6 0.2 263301:13 mongos
542 root 20 0 0 0 0 S 3.6 0.0 40:28.79 kswapd1
4 root 20 0 0 0 0 S 2.3 0.0 8869:27 ksoftirqd/0
33 root 20 0 0 0 0 S 2.0 0.0 4411:00 ksoftirqd/7
39893 root 20 0 2850m 34m 8084 S 2.0 0.0 262:43.09 osec_osta_agent
85 root 20 0 0 0 0 S 1.7 0.0 9155:36 ksoftirqd/20
113 root 20 0 0 0 0 S 1.7 0.0 4374:15 ksoftirqd/27
31563 tingfeng 20 0 2379m 43m 4188 S 1.7 0.0 1235:53 node_exporter
9 root 20 0 0 0 0 S 1.3 0.0 7210:33 ksoftirqd/1
13 root 20 0 0 0 0 S 1.3 0.0 6376:45 ksoftirqd/2
25 root 20 0 0 0 0 S 1.3 0.0 5072:24 ksoftirqd/5
89 root 20 0 0 0 0 S 1.3 0.0 7302:00 ksoftirqd/21
105 root 20 0 0 0 0 S 1.3 0.0 5126:01 ksoftirqd/25

top - 06:13:01 up 652 days, 16:14, 0 users, load average: 0.60, 0.39, 0.26
Tasks: 714 total, 1 running, 712 sleeping, 0 stopped, 1 zombie
Cpu(s): 0.7%us, 74.4%sy, 0.0%ni, 24.6%id, 0.0%wa, 0.0%hi, 0.3%si, 0.0%st
Mem: 131819804k total, 126711196k used, 5108608k free, 190928k buffers
Swap: 16777724k total, 0k used, 16777724k free, 61479556k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3249 root 20 0 2377m 432m 5744 S 3323.0 0.3 270938:54 mongos
5900 root 20 0 2341m 318m 5732 S 777.9 0.2 263301:37 mongos
3002 mongodb 20 0 1568m 386m 5336 S 3.6 0.3 43861:47 mongos
39893 root 20 0 2850m 35m 8084 S 1.7 0.0 262:43.14 osec_osta_agent
31866 mongodb 20 0 62.1g 57g 8232 S 1.0 45.4 74503:48 mongod
24663 root 20 0 15544 1744 920 R 0.7 0.0 346:50.50 top
4 root 20 0 0 0 0 S 0.3 0.0 8869:27 ksoftirqd/0
9 root 20 0 0 0 0 S 0.3 0.0 7210:33 ksoftirqd/1
113 root 20 0 0 0 0 S 0.3 0.0 4374:15 ksoftirqd/27
117 root 20 0 0 0 0 S 0.3 0.0 3765:47 ksoftirqd/28
32913 root 20 0 125m 23m 6720 S 0.3 0.0 678:49.79 agent
1 root 20 0 19356 1336 1012 S 0.0 0.0 1:01.95 init
2 root 20 0 0 0 0 S 0.0 0.0 0:00.10 kthreadd
3 root RT 0 0 0 0 S 0.0 0.0 4:16.03 migration/0
5 root RT 0 0 0 0 S 0.0 0.0 0:00.00 stopper/0
6 root RT 0 0 0 0 S 0.0 0.0 1:01.38 watchdog/0

top - 06:13:04 up 652 days, 16:14, 0 users, load average: 6.48, 1.61, 0.65
Tasks: 714 total, 1 running, 712 sleeping, 0 stopped, 1 zombie
Cpu(s): 0.8%us, 95.6%sy, 0.0%ni, 3.0%id, 0.0%wa, 0.0%hi, 0.5%si, 0.0%st
Mem: 131819804k total, 126686300k used, 5133504k free, 190936k buffers
Swap: 16777724k total, 0k used, 16777724k free, 61481400k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3249 root 20 0 2377m 453m 5744 S 2719.9 0.4 270940:16 mongos
5900 root 20 0 2341m 318m 5732 S 1024.2 0.2 263302:08 mongos
82 root RT 0 0 0 0 S 2.6 0.0 0:56.15 watchdog/19
3002 mongodb 20 0 1568m 386m 5336 S 2.6 0.3 43861:47 mongos
31866 mongodb 20 0 62.1g 57g 8232 S 2.0 45.4 74503:48 mongod
39893 root 20 0 2850m 34m 8084 S 1.7 0.0 262:43.19 osec_osta_agent
31563 tingfeng 20 0 2379m 44m 4188 S 1.0 0.0 1235:53 node_exporter
45 root 20 0 0 0 0 S 0.7 0.0 208:16.39 ksoftirqd/10
49 root 20 0 0 0 0 S 0.7 0.0 144:14.48 ksoftirqd/11
77 root 20 0 0 0 0 S 0.7 0.0 5:53.06 ksoftirqd/18
153 root 20 0 0 0 0 S 0.7 0.0 8:00.48 ksoftirqd/37
23455 root 20 0 0 0 0 S 0.7 0.0 25:14.61 flush-8:0
24663 root 20 0 15544 1744 920 R 0.7 0.0 346:50.52 top
32913 root 20 0 125m 23m 6720 S 0.7 0.0 678:49.81 agent
4 root 20 0 0 0 0 S 0.3 0.0 8869:27 ksoftirqd/0
9 root 20 0 0 0 0 S 0.3 0.0 7210:33 ksoftirqd/1
13 root 20 0 0 0 0 S 0.3 0.0 6376:45 ksoftirqd/2
17 root 20 0 0 0 0 S 0.3 0.0 5378:13 ksoftirqd/3
21 root 20 0 0 0 0 S 0.3 0.0 4083:40 ksoftirqd/4
25 root 20 0 0 0 0 S 0.3 0.0 5072:24 ksoftirqd/5

top - 06:13:07 up 652 days, 16:14, 0 users, load average: 6.48, 1.61, 0.65
Tasks: 714 total, 1 running, 712 sleeping, 0 stopped, 1 zombie
Cpu(s): 0.6%us, 98.6%sy, 0.0%ni, 0.5%id, 0.0%wa, 0.0%hi, 0.3%si, 0.0%st
Mem: 131819804k total, 126654344k used, 5165460k free, 190968k buffers
Swap: 16777724k total, 0k used, 16777724k free, 61483900k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3249 root 20 0 2377m 453m 5744 S 2821.5 0.4 270941:42 mongos
5900 root 20 0 2341m 318m 5732 S 963.5 0.2 263302:37 mongos
39893 root 20 0 2850m 34m 8084 S 1.3 0.0 262:43.23 osec_osta_agent
3002 mongodb 20 0 1568m 386m 5336 S 0.7 0.3 43861:47 mongos
24663 root 20 0 15544 1744 920 R 0.7 0.0 346:50.54 top
31866 mongodb 20 0 62.1g 57g 8232 S 0.7 45.4 74503:48 mongod
32913 root 20 0 125m 23m 6720 S 0.7 0.0 678:49.83 agent
35094 tingfeng 20 0 4452m 37m 3148 S 0.7 0.0 267:12.23 tingfeng-cli
4 root 20 0 0 0 0 S 0.3 0.0 8869:27 ksoftirqd/0
9 root 20 0 0 0 0 S 0.3 0.0 7210:33 ksoftirqd/1
65 root 20 0 0 0 0 S 0.3 0.0 8:52.01 ksoftirqd/15
69 root 20 0 0 0 0 S 0.3 0.0 6:57.76 ksoftirqd/16
73 root 20 0 0 0 0 S 0.3 0.0 6:10.23 ksoftirqd/17
121 root 20 0 0 0 0 S 0.3 0.0 3997:21 ksoftirqd/29
133 root 20 0 0 0 0 S 0.3 0.0 83:11.86 ksoftirqd/32
137 root 20 0 0 0 0 S 0.3 0.0 38:57.37 ksoftirqd/33
161 root 20 0 0 0 0 S 0.3 0.0 6:57.32 ksoftirqd/39
3924 root 20 0 18520 916 464 S 0.3 0.0 176:12.67 irqbalance
1 root 20 0 19356 1336 1012 S 0.0 0.0 1:01.95 init
2 root 20 0 0 0 0 S 0.0 0.0 0:00.10 kthreadd
3 root RT 0 0 0 0 S 0.0 0.0 4:16.03 migration/0
5 root RT 0 0 0 0 S 0.0 0.0 0:00.00 stopper/0
6 root RT 0 0 0 0 S 0.0 0.0 1:01.38 watchdog/0
7 root RT 0 0 0 0 S 0.0 0.0 3:08.17 migration/1

top - 06:13:10 up 652 days, 16:14, 0 users, load average: 10.36, 2.50, 0.94
Tasks: 714 total, 1 running, 712 sleeping, 0 stopped, 1 zombie
Cpu(s): 0.7%us, 98.2%sy, 0.0%ni, 0.8%id, 0.0%wa, 0.0%hi, 0.3%si, 0.0%st
Mem: 131819804k total, 126639648k used, 5180156k free, 190976k buffers
Swap: 16777724k total, 0k used, 16777724k free, 61486464k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3249 root 20 0 2377m 454m 5744 S 3968.9 0.4 270943:42 mongos
5900 root 20 0 2341m 318m 5732 S 1654.0 0.2 263303:27 mongos
31866 mongodb 20 0 62.1g 57g 8232 S 1.6 45.4 74503:48 mongod
32913 root 20 0 125m 23m 6720 S 1.6 0.0 678:49.88 agent
39893 root 20 0 2850m 34m 8084 S 1.6 0.0 262:43.28 osec_osta_agent
3002 mongodb 20 0 1568m 386m 5336 S 1.0 0.3 43861:47 mongos
24663 root 20 0 15544 1744 920 R 1.0 0.0 346:50.57 top
31563 tingfeng 20 0 2379m 43m 4188 S 1.0 0.0 1235:53 node_exporter
13 root 20 0 0 0 0 S 0.3 0.0 6376:45 ksoftirqd/2
21 root 20 0 0 0 0 S 0.3 0.0 4083:40 ksoftirqd/4
29 root 20 0 0 0 0 S 0.3 0.0 2711:07 ksoftirqd/6
37 root 20 0 0 0 0 S 0.3 0.0 3768:46 ksoftirqd/8
57 root 20 0 0 0 0 S 0.3 0.0 32:41.22 ksoftirqd/13
89 root 20 0 0 0 0 S 0.3 0.0 7302:00 ksoftirqd/21
93 root 20 0 0 0 0 S 0.3 0.0 6423:23 ksoftirqd/22
105 root 20 0 0 0 0 S 0.3 0.0 5126:01 ksoftirqd/25
117 root 20 0 0 0 0 S 0.3 0.0 3765:47 ksoftirqd/28
125 root 20 0 0 0 0 S 0.3 0.0 205:44.81 ksoftirqd/30
10831 root 20 0 4054m 325m 2568 S 0.3 0.3 269:43.52 java
1 root 20 0 19356 1336 1012 S 0.0 0.0 1:01.95 init
2 root 20 0 0 0 0 S 0.0 0.0 0:00.10 kthreadd
3 root RT 0 0 0 0 S 0.0 0.0 4:16.03 migration/0
4 root 20 0 0 0 0 S 0.0 0.0 8869:27 ksoftirqd/0

top - 06:13:13 up 652 days, 16:14, 0 users, load average: 14.42, 3.47, 1.27
Tasks: 714 total, 1 running, 712 sleeping, 0 stopped, 1 zombie
Cpu(s): 0.6%us, 98.3%sy, 0.0%ni, 0.7%id, 0.0%wa, 0.0%hi, 0.4%si, 0.0%st
Mem: 131819804k total, 126635428k used, 5184376k free, 190976k buffers
Swap: 16777724k total, 0k used, 16777724k free, 61489364k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3249 root 20 0 2377m 453m 5744 S 5460.0 0.4 270946:27 mongos
5900 root 20 0 2341m 318m 5732 S 2108.6 0.2 263304:31 mongos
31866 mongodb 20 0 62.1g 57g 8236 S 8.9 45.4 74503:49 mongod
3002 mongodb 20 0 1568m 386m 5336 S 5.0 0.3 43861:47 mongos
39893 root 20 0 2850m 34m 8084 S 2.0 0.0 262:43.34 osec_osta_agent
24663 root 20 0 15544 1744 920 R 0.7 0.0 346:50.59 top
32913 root 20 0 125m 23m 6720 S 0.7 0.0 678:49.90 agent
17 root 20 0 0 0 0 S 0.3 0.0 5378:13 ksoftirqd/3
29 root 20 0 0 0 0 S 0.3 0.0 2711:07 ksoftirqd/6
41 root 20 0 0 0 0 S 0.3 0.0 4026:59 ksoftirqd/9
49 root 20 0 0 0 0 S 0.3 0.0 144:14.49 ksoftirqd/11
53 root 20 0 0 0 0 S 0.3 0.0 70:02.14 ksoftirqd/12
61 root 20 0 0 0 0 S 0.3 0.0 15:21.65 ksoftirqd/14
77 root 20 0 0 0 0 S 0.3 0.0 5:53.07 ksoftirqd/18
81 root 20 0 0 0 0 S 0.3 0.0 5:40.61 ksoftirqd/19
97 root 20 0 0 0 0 S 0.3 0.0 5416:48 ksoftirqd/23
109 root 20 0 0 0 0 S 0.3 0.0 2723:55 ksoftirqd/26
149 root 20 0 0 0 0 S 0.3 0.0 8:44.48 ksoftirqd/36
157 root 20 0 0 0 0 S 0.3 0.0 7:17.41 ksoftirqd/38

top - 06:13:19 up 652 days, 16:14, 0 users, load average: 18.55, 4.51, 1.61
Tasks: 714 total, 1 running, 712 sleeping, 0 stopped, 1 zombie
Cpu(s): 0.7%us, 98.6%sy, 0.0%ni, 0.3%id, 0.0%wa, 0.0%hi, 0.4%si, 0.0%st
Mem: 131819804k total, 126641620k used, 5178184k free, 190984k buffers
Swap: 16777724k total, 0k used, 16777724k free, 61493904k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3249 root 20 0 2377m 453m 5744 S 8128.1 0.4 270950:34 mongos
5900 root 20 0 2341m 318m 5732 S 3047.9 0.2 263306:03 mongos
53 root 20 0 0 0 0 S 2.0 0.0 70:02.20 ksoftirqd/12
39893 root 20 0 2850m 34m 8084 S 1.6 0.0 262:43.44 osec_osta_agent
31563 tingfeng 20 0 2379m 43m 4188 S 1.0 0.0 1235:53 node_exporter
31866 mongodb 20 0 62.1g 57g 8236 S 1.0 45.4 74503:49 mongod
3002 mongodb 20 0 1568m 386m 5336 S 0.7 0.3 43861:47 mongos
24663 root 20 0 15544 1744 920 R 0.7 0.0 346:50.62 top
29241 tingfeng 20 0 4764m 44m 3460 S 0.7 0.0 293:15.35 ntp_exporter
9 root 20 0 0 0 0 S 0.3 0.0 7210:33 ksoftirqd/1
41 root 20 0 0 0 0 S 0.3 0.0 4026:59 ksoftirqd/9
45 root 20 0 0 0 0 S 0.3 0.0 208:16.40 ksoftirqd/10
65 root 20 0 0 0 0 S 0.3 0.0 8:52.02 ksoftirqd/15
69 root 20 0 0 0 0 S 0.3 0.0 6:57.77 ksoftirqd/16
97 root 20 0 0 0 0 S 0.3 0.0 5416:48 ksoftirqd/23
137 root 20 0 0 0 0 S 0.3 0.0 38:57.38 ksoftirqd/33

disk IO is very low, memory is enough

load and cpu monitor is :

net as following:

disk io as following: