When examining top, htop, or system monitoring tools on Linux systems, you'll encounter four primary CPU utilization metrics:

us: user time
sy: system time
ni: nice time
id: idle time

Nice time represents CPU cycles spent executing processes that have been manually assigned a non-default priority using the nice command or setpriority() system call. These processes run with adjusted scheduling priority (from -20 to 19, where lower numbers indicate higher priority).

Here's how to set process priority and observe nice time:

# Run a process with low priority
nice -n 19 ./long_running_script.sh

# Change priority of running process
renice +5 -p 1234

Monitoring nice time becomes particularly important when:

• Running background batch jobs
• Managing CPU-intensive tasks
• Optimizing system performance

Here's a Python script to monitor nice time percentage:

import psutil

def get_nice_time():
    cpu_times = psutil.cpu_times_percent(interval=1)
    return cpu_times.nice

print(f"Nice CPU time: {get_nice_time()}%")

High nice time percentages (consistently >10%) might indicate:

• Too many low-priority processes
• Incorrect priority assignments
• Potential system resource contention

To properly manage nice time:

1. Use nice for non-critical processes
2. Monitor nice time trends (sudden spikes may indicate issues)
3. Combine with I/O priority (ionice) for complete resource control

When monitoring system performance on Ubuntu servers or any Linux distribution, you'll encounter four primary CPU utilization metrics:

1. User - Time spent executing user-space processes
2. System - Time spent executing kernel-space processes  
3. Nice - Time spent executing low-priority (niced) processes
4. Idle - Time when CPU was not executing any tasks

The "Nice" value represents CPU cycles consumed by processes that have been intentionally assigned a lower priority using the nice command or setpriority() system call. These processes voluntarily yield CPU resources to more important tasks.

Here's how to set process priority using the nice command:

# Run a process with low priority (niceness +10)
nice -n 10 ./long_running_script.sh

# Change priority of running process (PID 1234)
renice +15 -p 1234

In C programming, you can adjust priority programmatically:

#include 
// Set current process to nice value of 10
setpriority(PRIO_PROCESS, 0, 10);

Common scenarios for niced processes include:

- Background batch jobs
- Data processing tasks
- Non-critical maintenance scripts
- CPU-intensive but low-priority computations

Use these commands to monitor nice CPU utilization:

# Basic CPU stats
mpstat -P ALL 1

# Detailed breakdown (including nice)
sar -u 1 3

# Process-level view with nice values
top -o %CPU

High nice CPU utilization typically indicates:

- System is properly prioritizing critical tasks
- Background processes are behaving as intended
- No immediate performance issues (unless nice % is extremely high)