Linux Cgroups

linux-cgroups

Purpose

This skill enables precise resource management for OpenClaw instances using Linux cgroups v2, focusing on memory limits, CPU quotas, OOM (Out-Of-Memory) protection, and systemd slices to prevent resource exhaustion and optimize performance on multi-process systems.

When to Use

Use this skill when running multiple OpenClaw instances on a Linux server to isolate resources, enforce limits on high-demand tasks, or protect against OOM kills in production environments. Apply it in scenarios with shared hosts, like containers or virtualized setups, to ensure fair CPU and memory allocation.

Key Capabilities

• Set memory limits to cap usage per OpenClaw instance, e.g., via memory.max to prevent swapping.
• Enforce CPU quotas using cpu.max for bandwidth control, limiting CPU time slices.
• Enable OOM protection with memory.oom.group to prioritize processes and avoid abrupt terminations.
• Manage systemd slices for hierarchical resource grouping, allowing nested cgroups for complex setups.

Usage Patterns

To apply cgroups, create a cgroup hierarchy, set limits, and assign processes. Always run as root or with sufficient privileges. For OpenClaw, wrap instance launches in cgroup contexts to enforce per-instance limits. Example: Create a slice for OpenClaw, then assign processes to it. Use Bash scripts for automation, checking cgroup paths under /sys/fs/cgroup/ for v2.

Common Commands/API

Interact with cgroups via CLI tools or directly via filesystem. No API keys needed; use system-level access.

• CLI Commands:
  • Create a cgroup: sudo cgcreate -g memory,cpu:/openclaw_slice
  • Set memory limit: sudo cgset -r memory.max=512M /openclaw_slice (limits to 512 MB)
  • Set CPU quota: sudo cgset -r cpu.max=100000 50000 /openclaw_slice (limits to 1 CPU core at 50% usage)
  • Execute process in cgroup: sudo cgexec -g memory,cpu:/openclaw_slice openclaw --run task
• Code Snippets (in Bash or Python):

  # Bash example to set and apply memory limit
  sudo cgcreate -g memory:/openclaw
  sudo cgset -r memory.max=1G /openclaw
  sudo cgexec -g memory:/openclaw openclaw --instance id1
  

  # Python snippet using subprocess (requires root)
  import subprocess
  subprocess.run(['cgcreate', '-g', 'memory:/openclaw'])
  subprocess.run(['cgset', '-r', 'memory.max=1G', '/openclaw'])
  subprocess.run(['cgexec', '-g', 'memory:/openclaw', 'openclaw', '--instance', 'id1'])
  

• Config Formats: Edit cgroup files directly, e.g., echo values to /sys/fs/cgroup/your_slice/memory.max. For systemd, define slices in .slice files under /etc/systemd/system/, like [Slice]\nMemoryMax=512M.

Integration Notes

Integrate with OpenClaw by wrapping commands in cgroup execution, e.g., modify startup scripts to include cgexec. Ensure the host uses cgroups v2 (check with stat /sys/fs/cgroup/unified); if v1, migrate via systemctl. For multi-instance setups, use environment variables like OPENCLAW_CGROUP_PATH=/openclaw_slice to pass cgroup details. Monitor usage with systemd-cgtop or cat /sys/fs/cgroup/your_slice/memory.current.

Error Handling

Common errors include permission denials (fix with sudo), invalid cgroup paths (verify with ls /sys/fs/cgroup/), or OOM events (check logs with dmesg | grep -i oom). Handle by:

• Checking return codes in scripts: if [ $? -ne 0 ]; then echo "Cgroup creation failed"; fi
• Monitoring memory pressure: Use cat /sys/fs/cgroup/your_slice/memory.oom_control and alert if OOM is triggered.
• Debugging: Run systemctl status your_slice for systemd slices; parse errors in code like:

  try:
      subprocess.run(['cgset', '-r', 'memory.max=1G', '/openclaw'], check=True)
  except subprocess.CalledProcessError as e:
      print(f"Error: {e.returncode} - {e.output}")
  

Concrete Usage Examples

1. Limit memory for a single OpenClaw instance: Create a cgroup slice, set a 2GB memory cap, and run the instance. Command sequence: sudo cgcreate -g memory:/openclaw_inst1; sudo cgset -r memory.max=2G /openclaw_inst1; sudo cgexec -g memory:/openclaw_inst1 openclaw --instance inst1 --task process_data. This prevents the instance from exceeding 2GB, avoiding OOM for other processes.
2. Apply CPU quota to multiple instances: Set a CPU limit for a group of OpenClaw tasks. Example: sudo cgcreate -g cpu:/openclaw_group; sudo cgset -r cpu.max=200000 100000 /openclaw_group; sudo cgexec -g cpu:/openclaw_group openclaw --instance inst2 --task compute_loop. This enforces a quota of 2 CPU cores at 50% each, ensuring balanced performance across instances.

Graph Relationships

• Related to: linux (cluster), as it builds on core Linux resource management.
• Connected via tags: cgroups (direct), memory (capability), limits (feature), performance (outcome).
• Links to other skills: cpu-management (for deeper CPU controls), oom-handler (for advanced OOM strategies).