What Does htop TIME+ Column Mean?

The htop interactive process viewer is a staple for Linux system administrators and power users monitoring system performance. When looking at the process list, you will notice a column labeled TIME+. This article explains exactly what the TIME+ column measures, how it differs from standard tools like ps, and how to interpret its value to identify resource-heavy applications.

Understanding the TIME+ Column

In htop, the TIME+ column measures the total CPU time a specific process has consumed since it was started.

It is a common misconception that this column represents the “wall-clock” elapsed time (how long the program has been running in real-world time). Instead, it strictly measures the duration the processor has spent executing instructions for that specific process.

Why the “+” Matters: Precision

If you are familiar with the standard top command, you might be used to seeing a TIME column. The addition of the plus sign (+) in htop represents a higher level of precision:

• Standard top (TIME): Typically measures CPU time in hundredths of a second or displays it in a MM:SS format.
• htop (TIME+): Measures CPU time with millisecond precision, formatted as MM:SS.hh (Minutes:Seconds.Hundredths of a second).

If a process has been running for a long time and consuming massive amounts of CPU, the format will automatically expand to include hours (HH:MM:SS.hh).

How CPU Time Accumulates

Because TIME+ measures actual processor utilization, the way time accumulates can sometimes seem counterintuitive:

• Idle Processes: If a text editor is left open for three hours but you aren’t typing, its wall-clock time is 3 hours, but its TIME+ value might only be a few seconds. It only accumulates time when the CPU is actively processing its tasks.
• Multi-threaded Processes: If a process utilizes multiple CPU cores simultaneously, it can accumulate CPU time faster than real-world time. For example, if a video rendering tool fully utilizes 4 CPU cores for exactly 10 seconds of real-world time, its TIME+ value will increase by roughly 40 seconds.

How to Use TIME+ for Troubleshooting

The TIME+ column is one of the best metrics for tracking down “stealthy” resource hogs. While the %CPU column tells you what is happening right now, the TIME+ column tells you the historical impact of a process.

• Spotting Background Drains: A background daemon might only use 2% of your CPU at any given millisecond (making it look innocent in the %CPU column), but if it runs constantly, its TIME+ value will be exceptionally high.
• Identifying Leaks: If two identical services were started at the same time, but one has a vastly higher TIME+ value, it indicates that specific instance is working significantly harder or is potentially stuck in an infinite loop.