118 lines
3.9 KiB
Markdown
118 lines
3.9 KiB
Markdown
# freeze-watcher
|
|
|
|
A systemd daemon that continuously samples Linux system state and dumps a detailed forensic snapshot whenever freeze-like conditions are detected (D-state spikes, PSI pressure, blocked processes, load avg). Includes a Qt GUI for live metrics and snapshot browsing.
|
|
|
|
Built to diagnose intermittent system freezes that don't show up in normal resource monitors — specifically the kind where some apps stall but the mouse keeps moving.
|
|
|
|
## What it captures
|
|
|
|
Each snapshot is a single text file in `/var/log/freeze-watcher/snap-YYYYMMDD-HHMMSS.log` containing:
|
|
|
|
- `loadavg`, `procs_running`, `procs_blocked`, `intr`, `ctxt`
|
|
- PSI cpu / io / memory pressure (`some` and `full` averages)
|
|
- D-state processes with kernel `wchan` (where exactly they're stuck)
|
|
- Top 15 by CPU and RSS
|
|
- `meminfo` summary
|
|
- `iostat -xt` snapshot
|
|
- Top interrupt sources by total + per-CPU breakdown
|
|
- Full `softirq` table
|
|
- Last 50 dmesg lines
|
|
- Last 60s of journal warnings/errors
|
|
|
|
The wchan column is the key one — that's how you tell `btrfs_lock_root_node` lock contention from `usb_sg_wait` USB stalls from `folio_wait_bit_common` page-fault stalls.
|
|
|
|
## Components
|
|
|
|
| Path | What |
|
|
|---|---|
|
|
| `src/freeze-watcher.sh` | The daemon — samples every 1s, captures on threshold |
|
|
| `src/freeze-monitor-gui` | PySide6 GUI: live metrics + snapshot browser + tray icon |
|
|
| `systemd/freeze-watcher.service` | systemd unit |
|
|
| `desktop/freeze-monitor.desktop` | App launcher entry |
|
|
|
|
## Install
|
|
|
|
### Via Makefile (system-wide install to `/usr/local`)
|
|
|
|
```
|
|
sudo make install
|
|
sudo make enable
|
|
```
|
|
|
|
### As an Arch package
|
|
|
|
```
|
|
./packaging/build-package.sh
|
|
sudo pacman -U freeze-watcher-*.pkg.tar.zst
|
|
sudo systemctl enable --now freeze-watcher.service
|
|
```
|
|
|
|
## Update workflow
|
|
|
|
When you change something:
|
|
|
|
```
|
|
# 1. Edit files in src/ or systemd/
|
|
# 2. Reinstall
|
|
sudo make install
|
|
|
|
# 3. If the daemon script changed, restart it
|
|
sudo systemctl restart freeze-watcher.service
|
|
|
|
# 4. If the GUI changed, just relaunch it (it's a regular Qt app)
|
|
```
|
|
|
|
If you're using the Arch package: `./packaging/build-package.sh && sudo pacman -U *.pkg.tar.zst` will rebuild and upgrade in place.
|
|
|
|
## Tuning thresholds
|
|
|
|
Open `src/freeze-watcher.sh` and edit the constants at the top:
|
|
|
|
```
|
|
PSI_IO_THRESHOLD=40 # io pressure avg10 % to trigger
|
|
PSI_CPU_THRESHOLD=50 # cpu pressure avg10 % to trigger
|
|
DSTATE_THRESHOLD=5 # processes in D state
|
|
BLOCKED_THRESHOLD=5 # procs_blocked from /proc/stat
|
|
LOAD_THRESHOLD=20 # 1-min load average
|
|
COOLDOWN=30 # seconds between captures
|
|
SAMPLE_INTERVAL=1 # seconds between samples
|
|
```
|
|
|
|
## GUI
|
|
|
|
Launch from app menu (search "Freeze Watcher") or `freeze-monitor-gui`.
|
|
|
|
- Live PSI / D-state / load metrics with green/orange/red color coding (1s refresh)
|
|
- Service status with start/stop buttons (uses `pkexec`)
|
|
- Captured event list — click any row for full snapshot view
|
|
- Closes to system tray; quit from the tray menu
|
|
- Notification when a new snapshot is captured
|
|
|
|
## Reading a snapshot
|
|
|
|
The most informative section is **D-state processes** — the `wchan` tells you what kernel function each process is blocked in. Common ones:
|
|
|
|
| wchan | Meaning |
|
|
|---|---|
|
|
| `btrfs_lock_root_node` | btrfs metadata lock contention (often qgroups + snapshots) |
|
|
| `btrfs_search_slot` | btrfs tree walk waiting for lock |
|
|
| `btrfs_sync_log` | fsync waiting for transaction commit |
|
|
| `folio_wait_bit_common` | Waiting for memory page (often swap-in) |
|
|
| `usb_sg_wait` | USB device stall |
|
|
| `io_schedule` | Generic I/O wait |
|
|
|
|
Cross-reference `wchan` with PSI io and PSI cpu to distinguish lock contention (low PSI) from genuine resource pressure (high PSI).
|
|
|
|
## Future ideas
|
|
|
|
- Per-cgroup PSI capture
|
|
- eBPF tracing for long-running syscalls
|
|
- Web UI option (no Qt requirement)
|
|
- Auto-prune old snapshots
|
|
- Configurable `/etc/freeze-watcher.conf` instead of inline thresholds
|
|
- Integration with desktop notifications via `notify-send`
|
|
- Optional perf-profile capture during event
|
|
|
|
## License
|
|
|
|
MIT
|