feat: dynamic CPU governor (performance during tasks, powersave at idle)

Switch to performance governor when task queue starts processing,
back to powersave when queue drains. Removes bee-cpuperf.service.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

audit/internal/webui/tasks.go

@@ -5,6 +5,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/http"
+	"os"
+	"path/filepath"
 	"sort"
 	"sync"
 	"time"
@@ -179,6 +181,7 @@ func (q *taskQueue) startWorker(opts *HandlerOptions) {
 func (q *taskQueue) worker() {
 	for {
 		<-q.trigger
+		setCPUGovernor("performance")
 		for {
 			q.mu.Lock()
 			t := q.nextPending()
@@ -211,6 +214,19 @@ func (q *taskQueue) worker() {
 			q.prune()
 			q.mu.Unlock()
 		}
+		setCPUGovernor("powersave")
+	}
+}
+
+// setCPUGovernor writes the given governor to all CPU scaling_governor sysfs files.
+// Silently ignores errors (e.g. when cpufreq is not available).
+func setCPUGovernor(governor string) {
+	matches, err := filepath.Glob("/sys/devices/system/cpu/cpu*/cpufreq/scaling_governor")
+	if err != nil || len(matches) == 0 {
+		return
+	}
+	for _, path := range matches {
+		_ = os.WriteFile(path, []byte(governor), 0644)
 	}
 }
 

iso/overlay/etc/systemd/system/bee-cpuperf.service

@@ -1,12 +0,0 @@
-[Unit]
-Description=Set CPU governor to performance
-DefaultDependencies=no
-After=sysinit.target
-
-[Service]
-Type=oneshot
-ExecStart=/bin/sh -c 'for f in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do [ -f "$f" ] && echo performance > "$f"; done'
-RemainAfterExit=yes
-
-[Install]
-WantedBy=multi-user.target

iso/overlay/etc/systemd/system/multi-user.target.wants/bee-cpuperf.service

@@ -1 +0,0 @@
-/etc/systemd/system/bee-cpuperf.service