Linux如何限制流程的資源使用情況

要限制Linux中進程的資源使用，應根據資源類型選擇合適工具：1. 使用ulimit限制單個進程的內存、文件大小、打開文件數和CPU時間，但不支持CPU或I/O帶寬限制；2. 使用cgroups（通過systemd-run或手動操作）實現對CPU、內存和I/O帶寬的精細控制，適用於現代系統並被Docker等容器技術採用；3. 使用nice調整進程CPU調度優先級，降低其在系統繁忙時的資源競爭能力，或使用cpulimit動態暫停進程以限制CPU使用率；4. 使用ionice設置I/O優先級，結合cgroups v2的io.max實現I/O帶寬硬限制；綜上，推薦systemd-run配合cgroups作為最簡潔的資源限制方案，ulimit適用於簡單場景，cpulimit適合快速限制CPU使用，最終選擇取決於系統版本和限制嚴格性需求。

If you need to limit the resource usage (CPU, memory, disk I/O, etc.) of a process in Linux, there are several built-in tools and mechanisms you can use. Here are the most practical and widely supported methods:

1. Using ulimit to restrict per-process resources

ulimit is a shell builtin that controls limits on resources for processes started from that shell. It's useful for setting limits like maximum memory, file size, number of open files, and CPU time.

Common usage:

 # Limit virtual memory to 500 MB
ulimit -v 512000

# Limit CPU time to 60 seconds
ulimit -t 60

# Limit max file size to 10 MB
ulimit -f 10240

# Limit number of open file descriptors
ulimit -n 256

Example:

 ulimit -v 512000
./your_program

⚠️ Note: ulimit only affects the current shell and child processes. It doesn't support CPU or I/O bandwidth limiting.

2. Using cgroups (Control Groups) for fine-grained control

For more advanced and flexible resource limiting (especially CPU and memory), use cgroups . Modern Linux systems use cgroups v2 , often managed via systemd or directly through the filesystem.

Option A: Using systemd-run (easiest for one-off processes)

 # Limit a process to 50% CPU and 500MB memory
systemd-run \
  --scope \
  --cpu-quota=50000% \
  --memory-limit=500M \
  ./your_program

• --cpu-quota=50000% means 50% of one CPU core (100% = 1 full core, so 50000% = 50%).
• --memory-limit=500M kills the process if it exceeds 500 MB.

Option B: Manual cgroups v2 (more control)

1. Create a cgroup:

    sudo mkdir /sys/fs/cgroup/limited

2. Set memory limit:

    echo 536870912 | sudo tee /sys/fs/cgroup/limited/memory.max # 512 MB

3. Set CPU limit (eg, 20% of one core):

    echo 20000 | sudo tee /sys/fs/cgroup/limited/cpu.max
   # Format: "max period" → "20000 100000" means 20% CPU
   echo "20000 100000" | sudo tee /sys/fs/cgroup/limited/cpu.max

4. Add a process to the cgroup:

    ./your_program &
   echo $! | sudo tee /sys/fs/cgroup/limited/cgroup.procs

This method is powerful and used by container runtimes like Docker.

3. Using nice and cpulimit for CPU control

nice – Adjust process scheduling priority

Doesn't limit CPU usage, but reduces priority so it gets less CPU when the system is busy.

 nice -n 19 ./your_program

• -n 19 is the lowest priority.

cpulimit – Actively limit CPU percentage

Install (if not available):

 sudo apt install cpulimit # Debian/Ubuntu

Limit a running process by name or PID:

 cpulimit -l 30 -p $(pgrep your_program)

Or launch a process with limit:

 cpulimit -l 30 -- ./your_program

cpulimit works by pausing the process using SIGSTOP / SIGCONT , so it's not perfectly smooth but effective.

4. Limiting disk I/O with ionice

Use ionice to control I/O priority (best effort, not hard limits).

 # Run with idle I/O priority (only uses disk when idle)
ionice -c 3 ./your_program

# Or low priority (class 2, level 7)
ionice -c 2 -n 7 ./your_program

For hard I/O rate limiting, use cgroups v2 with io.max (similar to memory/cpu limits).

Example:

 # Limit to 10 MB/s read, 5 MB/s write
echo "rbytes=10485760 wbytes=5242880" | sudo tee /sys/fs/cgroup/limited/io.max

Summary: Which tool to use?

For most users, systemd-run with cgroups is the cleanest way to limit CPU and memory. For scripting and simple cases, ulimit is sufficient. For older systems or quick CPU caps, cpulimit is handy.

Basically, it depends on your Linux version and how strict the limits need to be.

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