fix xmrig pause

services/xmrig-auto-pause.py

@@ -0,0 +1,131 @@
+#!/usr/bin/env python3
+"""
+Auto-pause xmrig when other services need CPU.
+
+Monitors non-nice CPU usage from /proc/stat. Since xmrig runs at Nice=19,
+its CPU time lands in the 'nice' column and is excluded from the metric.
+When real workload (user + system + irq + softirq) exceeds the threshold,
+stops xmrig. When it drops below threshold for GRACE_PERIOD seconds,
+restarts xmrig.
+
+This replaces per-service pause scripts with a single general-purpose
+monitor that handles any CPU-intensive workload (gitea workers, llama-cpp
+inference, etc.) without needing to know about specific processes.
+
+Why scheduler priority alone isn't enough:
+  Nice=19 / SCHED_IDLE only affects which thread gets the next time slice.
+  RandomX's 2MB-per-thread scratchpad (24MB across 12 threads) pollutes
+  the shared 32MB L3 cache, and its memory access pattern saturates DRAM
+  bandwidth. Other services run slower even though they aren't denied CPU
+  time. The only fix is to stop xmrig entirely when real work is happening.
+"""
+
+import os
+import subprocess
+import sys
+import time
+
+POLL_INTERVAL = int(os.environ.get("POLL_INTERVAL", "3"))
+GRACE_PERIOD = float(os.environ.get("GRACE_PERIOD", "15"))
+# Percentage of total CPU ticks that non-nice processes must use to trigger
+# a pause. On a 12-thread system, one fully loaded core ≈ 8.3% of total.
+# Default 5% catches anything using more than ~60% of a single core.
+CPU_THRESHOLD = float(os.environ.get("CPU_THRESHOLD", "5"))
+
+
+def log(msg):
+    print(f"[xmrig-auto-pause] {msg}", file=sys.stderr, flush=True)
+
+
+def read_cpu_ticks():
+    """Read CPU tick counters from /proc/stat.
+
+    Returns (total_ticks, real_work_ticks) where real_work excludes the
+    'nice' column (xmrig) and idle/iowait.
+    """
+    with open("/proc/stat") as f:
+        parts = f.readline().split()
+    # cpu  user nice system idle iowait irq softirq steal
+    user, nice, system, idle, iowait, irq, softirq, steal = (
+        int(x) for x in parts[1:9]
+    )
+    total = user + nice + system + idle + iowait + irq + softirq + steal
+    real_work = user + system + irq + softirq
+    return total, real_work
+
+
+def is_active(unit):
+    """Check if a systemd unit is currently active."""
+    result = subprocess.run(
+        ["systemctl", "is-active", "--quiet", unit],
+        capture_output=True,
+    )
+    return result.returncode == 0
+
+
+def systemctl(action, unit):
+    result = subprocess.run(
+        ["systemctl", action, unit],
+        capture_output=True,
+        text=True,
+    )
+    if result.returncode != 0:
+        log(f"systemctl {action} {unit} failed (rc={result.returncode}): {result.stderr.strip()}")
+    return result.returncode == 0
+
+
+def main():
+    paused_by_us = False
+    idle_since = None
+    prev_total = None
+    prev_work = None
+
+    log(f"Starting: poll={POLL_INTERVAL}s grace={GRACE_PERIOD}s threshold={CPU_THRESHOLD}%")
+
+    while True:
+        total, work = read_cpu_ticks()
+
+        if prev_total is None:
+            prev_total = total
+            prev_work = work
+            time.sleep(POLL_INTERVAL)
+            continue
+
+        dt = total - prev_total
+        if dt <= 0:
+            prev_total = total
+            prev_work = work
+            time.sleep(POLL_INTERVAL)
+            continue
+
+        real_work_pct = ((work - prev_work) / dt) * 100
+        prev_total = total
+        prev_work = work
+
+        busy = real_work_pct > CPU_THRESHOLD
+
+        if busy:
+            idle_since = None
+            if not paused_by_us:
+                # Only claim ownership if xmrig is actually running.
+                # If something else stopped it (e.g. UPS battery hook),
+                # don't interfere — we'd wrongly restart it later.
+                if is_active("xmrig.service"):
+                    log(f"Real workload detected ({real_work_pct:.1f}% CPU) — stopping xmrig")
+                    if systemctl("stop", "xmrig.service"):
+                        paused_by_us = True
+        else:
+            if paused_by_us:
+                if idle_since is None:
+                    idle_since = time.monotonic()
+                elif time.monotonic() - idle_since >= GRACE_PERIOD:
+                    log(f"Workload ended ({real_work_pct:.1f}% CPU) past grace period — starting xmrig")
+                    if systemctl("start", "xmrig.service"):
+                        paused_by_us = False
+                    idle_since = None
+
+        time.sleep(POLL_INTERVAL)
+
+
+if __name__ == "__main__":
+    main()