# auto_suspend — Idle-based System Suspend Auto-suspend monitors a system's CPU and GPU utilization, applies exponential moving average (EMA) smoothing, and suspends the machine when idle for a configured period. **Target platform:** RHEL/EL 9 with SELinux enforcing (Fedora/RHEL datacenter GPUs) --- ## Goal Automatically put idle GPU workstations into suspend (RAM sleep) to save power and reduce heat, while ensuring no user session or active workload is interrupted. The system checks every 5 minutes. It suspends only after `idle_timeout_cycles` consecutive checks confirm the system is idle, using EMA-smoothed metrics to avoid false positives from transient spikes. --- ## Architecture ``` ┌─────────────┐ every 5 min ┌──────────────────┐ │ timer │ ────────────────────▶ │ service │ │ auto-suspend│ │ auto-suspend │ └─────────────┘ └────────┬─────────┘ │ measures: cpu, nvidia, amd │ EMA smoothing + warmup check │ evaluate idle? ╱ ╲ yes ╱ ╲ no │ │ ▼ ▼ idle_counter++ idle_counter=0 │ counter ≥ 4? ╱ ╲ yes ╱ ╲ no │ │ ▼ ▼ systemctl re-persist suspend state.json ``` ### Key design decisions - **State persists across timer invocations** — `state.json` carries EMA averages, idle counter, and sample count between checks. The system can accumulate 20+ minutes of data across reboots (state survives suspend). - **Any busy GPU prevents suspend** — max utilization across all NVIDIA + AMD GPUs is used. One busy GPU = no suspend. - **Reset on resume** — after `systemctl suspend`, state is fully reset so the warmup period starts fresh. - **GPU presence is optional** — `None` from a GPU driver means "no GPU of this type", which does NOT block suspend. --- ## Directory Structure ``` ansible/roles/auto_suspend/ ├── defaults/main.yml # Configurable parameters (tunable via inventory/host_vars) ├── meta/main.yml # Galaxy metadata └── tasks/ │ └── main.yml # Ansible tasks (dependencies, scripts, systemd, SELinux) └── files/ ├── auto_suspend.py # Main Python daemon (522 lines) ├── test_auto_suspend.py # Unit tests (48 tests, stdlib only) └── fixtures/ # Real command samples from gpu-01 ├── amd-smi-monitor--json.txt ├── mpstat--1--1.idle.txt ├── nvidia-smi--query-gpu.utilization.gpu.csv.noheader.idle.txt └── who.with-users.txt ``` --- ## Playbook Usage ```yaml # ansible/playbook_auto_suspend.yml - name: Setup Auto Suspend hosts: auto_suspend roles: - auto_suspend ``` Deploy via: ```bash cd ansible/ sectool -f ../sectool.json exec ansible-playbook -u $ANSIBLE_USER playbook_auto_suspend.yml ``` The `auto_suspend` inventory group currently contains only `gpu-01.lab.alexpires.me`. --- ## Configuration (defaults/main.yml) | Variable | Default | Description | |---|---|---| | `auto_suspend_alpha` | `0.3` | EMA weight for current sample (0.3 = 30% current, 70% historical) | | `auto_suspend_min_samples` | `3` | Warmup checks before trust (3 × 5 min = 15 min minimum) | | `auto_suspend_idle_timeout_cycles` | `4` | Consecutive idle checks before suspend (4 × 5 min = 20 min total) | | `auto_suspend_cpu_idle_threshold` | `90.0` | CPU idle % must exceed this to count as idle | | `auto_suspend_gpu_util_threshold` | `5.0` | GPU util % must be below this to count as idle | | `auto_suspend_state_dir` | `/var/lib/auto_suspend` | Directory for state.json persistence | | `auto_suspend_log_file` | `/var/log/auto_suspend.log` | Log file path (RotatingFileHandler, 1 MB × 3 backups) | | `auto_suspend_grub_config_path_bios` | `/boot/grub2/grub.cfg` | GRUB config output path for BIOS systems | All variables can be overridden via inventory, group_vars, or host_vars. --- ## Deployed Artifacts | Path | Type | Purpose | |---|---|---| | `/usr/local/bin/auto_suspend.py` | Python script | Main daemon, copied from `files/auto_suspend.py` | | `/etc/systemd/system/auto-suspend.service` | systemd oneshot | Runs the check + suspend logic | | `/etc/systemd/system/auto-suspend.timer` | systemd timer | Triggers service every 5 minutes (5 min after boot) | | `/etc/systemd/sleep.conf.d/mem-deep.conf` | sysctl override | Sets `MemorySleepMode=deep` | | `/var/lib/auto_suspend/state.json` | JSON | EMA state, idle counter, sample count | | `/var/log/auto_suspend.log` | log | Rotating log (1 MB, 3 backups) | --- ## auto_suspend.py — Script Reference ### CLI Arguments All arguments map directly to `defaults/main.yml` variables: ``` --alpha 0.3 EMA smoothing factor --min-samples 3 Warmup period --idle-timeout-cycles 4 Consecutive idle checks needed --cpu-idle-threshold 90.0 CPU idle % threshold --gpu-util-threshold 5.0 GPU util % threshold --state-dir /var/lib/auto_suspend --log-file /var/log/auto_suspend.log --debug Enable debug-level logging --dry-run Run check without persisting state or suspending ``` ### Public Functions | Function | Returns | Purpose | |---|---|---| | `setup_logging(log_file, debug)` | `logging.Logger` | Configures file + stderr handlers | | `fresh_state()` | `dict` | Returns default state with all values at initial values | | `load_state(state_dir, logger)` | `dict` | Loads state from disk, returns fresh on any error | | `save_state(state_dir, state, logger)` | `None` | Atomic write via temp file + os.replace | | `measure_cpu(logger)` | `float \| None` | Runs `mpstat 1 1`, returns %idle | | `measure_gpu_nvidia(logger)` | `float \| None` | Runs `nvidia-smi`, returns max util across all GPUs | | `measure_gpu_amd(logger)` | `float \| None` | Runs `amd-smi monitor --json`, returns gfx.value of GPU 0 | | `get_active_users(logger)` | `int` | Parses `who` output, returns non-empty line count | | `get_why_not_idle(cpu_avg, gpu_avg, sample_count, idle_counter, has_users, cpu_threshold, gpu_threshold)` | `list[str]` | Returns human-readable reasons why system is not idle | | `update_averages(state, cpu_n, gpu_n, alpha)` | `dict` | EMA update: returns new state with averaged values | | `evaluate(state, has_users, cpu_threshold, gpu_threshold)` | `bool` | Gate checks: warmup → users → CPU → GPU | | `signal_handler(signum, frame)` | `NoReturn` | SIGTERM/SIGINT handler, calls `sys.exit(0)` | | `main()` | `NoReturn` | Entry point: measures, evaluates, updates state, suspends | ### State Schema (`state.json`) ```json { "cpu_idle_n": null, // latest CPU idle % (current sample) "cpu_idle_n1": null, // latest CPU idle % (previous sample, n-1) "gpu_util_n": null, // latest GPU util % (current sample) "gpu_util_n1": null, // latest GPU util % (previous sample, n-1) "cpu_avg": null, // EMA-smoothed CPU idle average "gpu_avg": null, // EMA-smoothed GPU utilization average "idle_counter": 0, // consecutive idle cycles "sample_count": 0 // total samples collected } ``` ### EMA Formula ``` EMA_new = alpha * current_sample + (1 - alpha) * previous_EMA ``` With `alpha=0.3`: 30% weight on the current reading, 70% on the historical average. `round(..., 2)` keeps precision to 2 decimal places. ### GPU Detection **NVIDIA** — `nvidia-smi --query-gpu=utilization.gpu --format=csv,noheader,nounits` - Parses each line as float, returns `max()` across all GPUs - Returns `None` if nvidia-smi is missing, fails, or times out - `None` means no NVIDIA GPU present (does NOT block suspend) **AMD** — `amd-smi monitor --json` - Parses `data[0]["gfx"]["value"]` from first GPU - Handles both `{"value": N, "unit": "%"}` and raw numeric `gfx` formats - Returns `None` if amd-smi is missing, fails, or times out **Combined** — `max()` across all non-None GPU measurements. Any busy GPU prevents suspend. ### Suspend Decision Logic (evaluate) Four gates in order: 1. **Warmup** — If `sample_count < min_samples`, return `False` (skip evaluation) 2. **Active users** — If `who` returns non-empty output, return `False` 3. **CPU idle** — If `cpu_avg > cpu_threshold` is False, return `False` 4. **GPU idle** — If GPU is present (`gpu_avg is not None`) and `gpu_avg >= gpu_threshold`, return `False` Only when all gates pass does `idle_counter` increment. When `idle_counter >= idle_timeout_cycles`, `systemctl suspend` is called. On failure to suspend, `idle_counter` resets to 0. ### Dry-Run Mode `--dry-run` runs all measurement, EMA, and evaluation logic but: - Does NOT persist state to disk - Does NOT call `systemctl suspend` - Prints `Would suspend: idle timeout reached (idle_counter=X/Y)` instead --- ## Unit Tests (`test_auto_suspend.py`) 48 tests covering all public functions using `unittest` + `unittest.mock`. ### Test Classes | Class | Tests | Coverage | |---|---|---| | `TestFreshState` | 1 | Returns correct defaults | | `TestLoadState` | 4 | Missing file, valid JSON, invalid JSON, missing keys merged | | `TestSaveState` | 3 | Atomic write, parent dir creation, no leftover tmp | | `TestMeasureCpu` | 4 | Idle, busy, non-zero exit, timeout | | `TestMeasureGpuNvidia` | 6 | Idle, busy single, multi-GPU max, file not found, timeout, non-zero exit | | `TestMeasureGpuAmd` | 7 | Busy, idle, medium, file not found, short output, empty array, non-zero exit | | `TestGetActiveUsers` | 3 | No users, with users, timeout | | `TestUpdateAverages` | 4 | First sample, EMA calc, n→n1 shift, None preservation | | `TestEvaluate` | 10 | Idle system, warmup skip, users, CPU not idle, GPU busy, GPU None, at threshold CPU, at threshold GPU, custom thresholds | | `TestGetWhyNotIdle` | 5 | Users, CPU low, GPU high, warming up, multiple reasons | | `TestSetupLogging` | 1 | Returns logger with handlers | | `TestSignalHandler` | 1 | Returns exit code 0 | ### Running Tests ```bash cd ansible/roles/auto_suspend python3 -m pytest files/test_auto_suspend.py -v # or python3 files/test_auto_suspend.py ``` Tests use `unittest.mock.patch("auto_suspend.subprocess.run")` to intercept all subprocess calls. Fixture data comes from real command outputs on gpu-01. --- ## Making Changes ### Modifying the Python Script (`files/auto_suspend.py`) 1. Edit `files/auto_suspend.py` 2. Add or update tests in `files/test_auto_suspend.py` — mock `subprocess.run` with `MagicMock(returncode=..., stdout=..., stderr=...)` 3. Add new fixtures to `files/fixtures/` if you need new command output samples 4. Run `python3 -m pytest files/test_auto_suspend.py -v` — all 48 tests must pass 5. Deploy to gpu-01 and verify with `journalctl -u auto-suspend.service` ### Modifying Ansible Tasks (`tasks/main.yml`) The role uses inline content for systemd unit files (no `templates/` directory). To change systemd configuration, edit the inline YAML in the relevant `ansible.builtin.copy` task. Key tasks in order: 1. Install dependencies (`sysstat`, `python3`) 2. Enable sysstat service 3. Set GRUB `mem_sleep_default=deep` (BIOS only) 4. Create state directory + log file 5. Copy Python script 6. Set SELinux context (`bin_t` + `restorecon`) 7. Create systemd service (inline) 8. Create sleep.conf.d deep sleep override 9. Create systemd timer (inline) 10. Reload systemd daemon 11. Enable + start timer 12. Verify with `--dry-run` ### Adding a New GPU Vendor 1. Add `measure_gpu_(logger)` in `auto_suspend.py` following the existing pattern (return `float` utilization or `None`) 2. Wire it into `main()`: ```python gpu_ = measure_gpu_(logger) gpu_values = [v for v in [gpu_nvidia, gpu_amd, gpu_] if v is not None] gpu_util = max(gpu_values) if gpu_values else None ``` 3. Add CLI argument if vendor-specific threshold is needed 4. Add fixtures for test data 5. Add `TestMeasureGpu` test class ### Overriding Defaults All defaults in `defaults/main.yml` can be overridden via: - Inventory: `group_vars/auto_suspend.yml` - Host vars: `host_vars/gpu-01.lab.alexpires.me.yml` - Command line: `ansible-playbook ... -e "auto_suspend_alpha=0.5"` --- ## SELinux On EL 9 with SELinux enforcing, the Python script in `/usr/local/bin/` needs `bin_t` context: ```yaml - name: Set SELinux file context on script community.general.sefcontext: path: /usr/local/bin/auto_suspend.py setype: bin_t state: present failed_when: false - name: Restore SELinux context on script ansible.builtin.command: restorecon -v /usr/local/bin/auto_suspend.py failed_when: false ``` Both tasks use `failed_when: false` to tolerate systems where SELinux is disabled or the context is already correct. Requires `community.general` Ansible collection. --- ## Systemd Configuration ### auto-suspend.service - `Type=oneshot` — runs once per timer tick - `Restart=on-failure`, `RestartSec=30` — retries on error - Passes all config as CLI flags (not via environment) ### auto-suspend.timer - `OnBootSec=5min` — first run 5 minutes after boot - `OnUnitActiveSec=5min` — subsequent runs every 5 minutes - `Unit=auto-suspend.service` ### sleep.conf.d `/etc/systemd/sleep.conf.d/mem-deep.conf` sets `MemorySleepMode=deep` to ensure deep sleep state (lowest power consumption). ### GRUB The role ensures `mem_sleep_default=deep` is present in `GRUB_CMDLINE_LINUX` and regenerates the GRUB config. This is BIOS-specific (UEFI is not currently supported). --- ## Hardware Target The role was developed for `gpu-01.lab.alexpires.me`: - Fedora 42 (kernel 6.17.11), 12-core x86_64 - NVIDIA GPU + AMD GPU (dual-GPU system) - SELinux enforcing - Used for AI inference (Ollama, ComfyUI, llama.cpp, Qwen) - Network-accessible workstation --- ## Troubleshooting ### Check service status ```bash systemctl status auto-suspend.service systemctl status auto-suspend.timer ``` ### View logs ```bash journalctl -u auto-suspend.service --no-pager cat /var/log/auto_suspend.log ``` ### Run a manual check ```bash /usr/local/bin/auto_suspend.py --dry-run --debug ``` ### Check state ```bash cat /var/lib/auto_suspend/state.json ``` ### Force a timer run ```bash systemctl start auto-suspend.service ``` ### Re-deploy after changes ```bash cd ansible/ sectool -f ../sectool.json exec ansible-playbook -u $ANSIBLE_USER playbook_auto_suspend.yml ```