是否应调低用户进程的nice值甚至设为最低以加快运行速度？

Great question—let’s break this down clearly, since nice values are one of those Unix-like system tools that seem simple at first but have key nuances depending on your system’s state.

First, a quick recap to make sure we’re on the same page: On most systems, nice values range from -20 (highest priority) to 19 (lowest priority). When you "lower" a process’s nice value (e.g., from the default 0 to -10, or even -20), you’re telling the kernel to prioritize that process for CPU time over others with higher (less favorable) nice values.

Now, the answer depends entirely on whether your system is under CPU load:

When it will speed up your process #

If your system is running multiple CPU-intensive tasks and the CPU is at or near 100% utilization, lowering the nice value will absolutely make your target process run faster. The kernel will allocate a larger share of CPU cycles to your high-priority process, letting it finish quicker while deprioritizing less important tasks. This is perfect for things like video encoding, large data crunching, or any task where you want to throw as much CPU as possible at it while other background processes run.

When it won’t make a difference #

If your system is idle, or the CPU isn’t being fully used by other processes, lowering the nice value won’t give you any noticeable speed boost. Your process was already getting all the CPU time it needed—there’s no extra cycles to reallocate. It’s like asking for a bigger slice of pizza when you’re already eating the whole pie by yourself.

A few key caveats to remember #

• Permissions matter: Regular users can only increase the nice value of their own processes (making them lower priority). To lower the nice value (boost priority), you need root privileges. For example, start a process with high priority using sudo nice -n -10 ./your-program, or adjust a running process with sudo renice -n -10 <pid>.
• Only helps CPU-bound processes: If your program spends most of its time waiting on disk I/O, network requests, or user input, even the highest CPU priority won’t speed it up. The bottleneck isn’t the CPU—you’d need to optimize those other areas instead.

So to sum it up: Lowering the nice value speeds up your process only when there’s active competition for CPU resources. On an idle system, it’s a change you won’t even notice.

内容的提问来源于stack exchange，提问作者Nagri