Ubuntu Touch's ssh service will have a lag problem, which can actually be alleviated by increasing the ssh connection priority through the nice value

Process priority nice

• Linux process scheduling and multitasking
• Relative priority nice
• View the nice level of the process
• Start processes with different nice levels
• Change the nice level of an existing process

Linux Process Scheduling and Multitasking

Each CPU (or CPU core) can only process one process at a time point. Through the time slice technology, the actual number of processes (and threads) that Linux can run can
The actual available CPU and coresquantity.The Linux kernel Process scheduler quickly switches multiple processes on the CPU core, giving the user the impression that multiple processes are running at the same time.

relative priority nice

Since not every process is as important as others, tell the Process Scheduler to use different scheduling strategies for different processes.The scheduling policy used by most
processes running on regular systems is SCHED_OTHER (also known as SCHED_NORMAL), but there are other scheduling policies for different purposes.

The relative priority of the process run by the

SCHED_OTHER scheduling policy is called the nice value of the process, and there can be 40 different levels of nice value.

Higher value of nice: means lower priority, eg +19, the process tends to cede CPU usage to other processes.

The lower the nice value: the higher the priority, eg -20, the less likely the process is to give up the CPU.

View the nice level of the process

1. Use top to view nice level
NI: actual nice level
PR: show nice level as mapped to larger priority queue, -20 to 0, +19 to 39

3. Use ps to check the nice level
[[email protected] ~]# ps axo pid,command,nice --sort=-nice
[[email protected] ~]# ps axo pid,command,nice,cls --sort=-nice
TS indicates that the scheduling policy used by the process is SCHED_OTHER

Start processes with different nice levels

When starting a process, it usually inherits the nice level of the parent process, which defaults to 0.
[[email protected] ~]# nice -n -5 sleep 6000 &
[[email protected] ~]# ps axo command,pid,nice |grep sleep

[[email protected] ~]# nice -n -20 service httpd start
[[email protected] ~]# ps axo pid,command,nice,cls |grep httpd
11116 /usr/sbin/httpd-20 TS
11119 /usr/sbin/httpd -20 TS
11120 /usr/sbin/httpd -20 TS
11121 /usr/sbin/httpd -20 TS
11122 /usr/sbin/httpd -20 TS
11123 /usr/sbin/httpd -20 TS
11124 /usr/sbin/httpd -20 TS
11125 /usr/sbin/httpd -20 TS
11126 /usr/sbin/httpd -20 TS

Change the nice level of an existing process

1. Use top to change the nice level
r Adjust the priority of the process (Nice Level) (-20 high) －－－0－－－ (19 low)

2. Change nice level using shell
[[email protected] ~]# sleep 7000 &
[3] 10089
[[email protected] ~]# renice -20 10089
10089: oldpriority 0, new priority -20