For common process management tasks, top is so great because it gives an overview of the most active processes currently running (hence the name top). This enables you to easily find processes that might need attention. From top, you can also perform common process management tasks, such as adjusting the current process priority and killing processes.
[root@rhel7 ~]# top top - 22:58:17 up 27 min, 1 user, load average: 0.00, 0.01, 0.05 Tasks: 88 total, 2 running, 86 sleeping, 0 stopped, 0 zombie %Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem : 1884188 total, 1651932 free, 85420 used, 146836 buff/cache KiB Swap: 2097148 total, 2097148 free, 0 used. 1654104 avail Mem PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1 root 20 0 44500 7104 2584 S 0.0 0.4 0:01.61 systemd 2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd 3 root 20 0 0 0 0 S 0.0 0.0 0:00.01 ksoftirqd/0 7 root rt 0 0 0 0 S 0.0 0.0 0:00.00 migration/0 8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_bh 9 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcuob/0 10 root 20 0 0 0 0 S 0.0 0.0 0:00.66 rcu_sched 11 root 20 0 0 0 0 R 0.0 0.0 0:00.30 rcuos/0 12 root rt 0 0 0 0 S 0.0 0.0 0:00.02 watchdog/0 13 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 khelper 14 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kdevtmpfs 15 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 netns 16 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 perf 17 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 writeback 18 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kintegrityd 19 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 bioset 20 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kblockd 21 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 md 22 root 20 0 0 0 0 S 0.0 0.0 0:01.04 kworker/0:1 26 root 20 0 0 0 0 S 0.0 0.0 0:00.00 khungtaskd 27 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kswapd0 28 root 25 5 0 0 0 S 0.0 0.0 0:00.00 ksmd 29 root 39 19 0 0 0 S 0.0 0.0 0:00.01 khugepaged 30 root 20 0 0 0 0 S 0.0 0.0 0:00.00 fsnotify_mark 31 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 crypto 39 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kthrotld 41 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kmpath_rdacd 42 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kpsmoused 43 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 ipv6_addrconf 63 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 deferwq 93 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kauditd 253 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 ata_sff
Now that you know how to use the kill and nice commands from the command line, using the same functionality from top is even easier. From top, type k . top will then prompt for the PID of the process you want to send a signal to. By default, the most active process is selected. After you enter the PID, top asks which signal you want to send. By default, signal 15 for SIGTERM is used. However, if you want to insist a bit more, you can type 9 for SIGKILL. Now press Enter to terminate the process.
To renice a running process from top, type r . You are first prompted for the PID of the process you want to renice. After entering the PID, you are prompted for the nice value you want to use. Enter a positive value to increase process priority or a negative value to decrease process priority.