Redesign approach for CPU usage tracking
The previous implementation maintained three exponential moving averages (1/5/15-minute) of CPU busy-fraction, sampled every 5 seconds. This had two problems: 1. Wrong semantics: the metric was labelled "load_avg" (a Unix concept measuring run-queue depth), but the tracker actually measures CPU busy-time as a fraction of FreeRTOS ticks — i.e. utilization, not load. The name was misleading. 2. Poor responsiveness: the 1-minute EMA (DECAY = exp(-5/60) ≈ 0.920) has a ~60-second time constant. On a live web panel, this made the metric appear frozen, especially during short bursts of activity (e.g. an HTTP request from the panel itself). This commit replaces the EMA with a 64-sample simple moving average (SMA) over a compact uint8_t circular buffer. The sample interval is 60 s / 64 = 937,500 µs, so the window covers exactly 60 seconds: Algorithm: - Every 937,500 µs (= 60 s / 64), the FreeRTOS tick delta (busy vs idle ticks on core 0) is computed and stored as a uint8_t (0–255 = 0–100% utilization). - The circular buffer holds 64 samples, spanning exactly 60 seconds (64 × 937,500 µs = 60,000,000 µs). The timer interval is derived directly from the window size: 60 000 000 / SMA_WINDOW µs. - The index wraps with a bitwise AND (& 63) instead of modulo, since 64 is a power of 2. - The running sum is a uint16_t (max 64 × 255 = 16 320, fits easily). - The result _sma_avg is a volatile float written atomically by the esp_timer task (core 0) and read from the main loop (core 1). No spinlock is needed: on Xtensa LX7, a 32-bit aligned float store is a single instruction. The 60-second window smooths out short bursts (e.g. WiFi/HTTP spikes) while reacting to sustained load changes within ~10–15 seconds. Naming: - The public API is now getCore0Util() returning a float in [0.0, 1.0]. The name explicitly identifies which core is measured (core 0, which runs WiFi, MQTT, HTTP, and LwIP — see task_pinning.c). - JSON keys: "load_avg" (array) → "core0_util" (scalar float, percent) - HistorySample field: load_avg1_pct → core0_util_pct - StatsHistory series key: "cpu_load" → "core0_util" - Web panel label: "Load Avg" → "Core0 Util" The history snapshot (once per minute) reads the same _sma_avg value, which at that point represents the rolling average of the last 60 seconds — exactly one history interval.
This commit is contained in:
Valentin V. Bartenev
@@ -211,8 +211,8 @@ bool buildPointValue(const HistorySample& sample, const HistorySample* previous,
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value = static_cast<int>(sample.battery_mv);
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return true;
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}
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if (strcmp(series, "cpu_load") == 0) {
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value = static_cast<int>(sample.load_avg1_pct);
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if (strcmp(series, "core0_util") == 0) {
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value = static_cast<int>(sample.core0_util_pct);
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return true;
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}
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if (strcmp(series, "memory") == 0) {
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@@ -313,8 +313,8 @@ const char* seriesTitle(const char* series) {
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if (strcmp(series, "battery") == 0) {
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return "Battery";
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}
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if (strcmp(series, "cpu_load") == 0) {
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return "CPU Load";
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if (strcmp(series, "core0_util") == 0) {
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return "Core0 Util";
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}
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if (strcmp(series, "memory") == 0) {
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return "Heap Free";
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@@ -362,7 +362,7 @@ const char* seriesUnit(const char* series) {
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if (strcmp(series, "battery") == 0) {
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return "mV";
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}
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if (strcmp(series, "cpu_load") == 0) {
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if (strcmp(series, "core0_util") == 0) {
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return "pct";
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}
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if (strcmp(series, "memory") == 0) {
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@@ -649,7 +649,7 @@ bool StatsHistory::parseSummaryLine(const char* line, HistorySample& sample) con
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long gps_lon_e6 = 0;
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unsigned sensor_flags = 0;
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unsigned gps_satellites = 0;
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unsigned load_avg1_pct = 0;
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unsigned core0_util_pct = 0;
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int parsed = sscanf(line,
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"%lu,%lu,%u,%u,%d,%d,%d,%lu,%lu,%lu,%lu,%u,%u,%u,%u,%u,%u,%u,%d,%d,%u,%u,%d,%d,%ld,%ld,%u,%u,%u",
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@@ -681,7 +681,7 @@ bool StatsHistory::parseSummaryLine(const char* line, HistorySample& sample) con
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&gps_lon_e6,
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&sensor_flags,
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&gps_satellites,
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&load_avg1_pct);
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&core0_util_pct);
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if (parsed == 29 || parsed == 28) {
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memset(&sample, 0, sizeof(sample));
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sample.epoch_secs = static_cast<uint32_t>(epoch_secs);
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@@ -715,7 +715,7 @@ bool StatsHistory::parseSummaryLine(const char* line, HistorySample& sample) con
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sample.gps_satellites = static_cast<uint8_t>(gps_satellites);
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sample.flags = static_cast<uint8_t>(flags);
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sample.battery_pct = -1;
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sample.load_avg1_pct = (parsed == 29) ? static_cast<uint8_t>(load_avg1_pct) : 0;
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sample.core0_util_pct = (parsed == 29) ? static_cast<uint8_t>(core0_util_pct) : 0;
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return true;
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}
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@@ -1129,7 +1129,7 @@ void StatsHistory::flushSummaryLog() {
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static_cast<long>(latest.gps_lon_e6),
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static_cast<unsigned>(latest.sensor_flags),
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static_cast<unsigned>(latest.gps_satellites),
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static_cast<unsigned>(latest.load_avg1_pct));
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static_cast<unsigned>(latest.core0_util_pct));
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File latest_file = openArchiveWriteWithRecovery(_archive, kSummaryLatestPath);
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if (!latest_file) {
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@@ -37,7 +37,7 @@ struct HistorySample {
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uint8_t gps_satellites;
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uint8_t flags;
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int8_t battery_pct;
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uint8_t load_avg1_pct;
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uint8_t core0_util_pct;
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};
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struct HistoryEvent {
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@@ -531,8 +531,6 @@ const char kWebPanelAppHtml[] PROGMEM = R"HTML(
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:root[data-theme="dark"] .metric { background:rgba(0,0,0,.16); }
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.metric-label { font-size:11px; color:var(--text-muted); text-transform:uppercase; letter-spacing:.06em; }
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.metric-value { margin-top:4px; font-size:16px; font-weight:700; color:var(--text); }
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.metric-spread { display:flex; justify-content:space-between; margin-top:4px; }
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.metric-spread span { font-size:16px; font-weight:700; color:var(--text); }
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.events-table-wrap { overflow-x:auto; border:1px solid var(--border); border-radius:12px; }
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.events-table { width:100%; border-collapse:collapse; }
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.events-table th, .events-table td { padding:10px 12px; text-align:left; font-size:13px; }
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@@ -1490,14 +1488,7 @@ const char kWebPanelAppHtml[] PROGMEM = R"HTML(
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<div class="metric-grid core-metrics">
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${renderMetric("Uptime", formatDuration(core.uptime_secs))}
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${renderMetric("Battery", (core.battery_mv || 0) + " mV")}
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${Array.isArray(core.load_avg) ? `<div class="metric">
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<div class="metric-label">Load Avg</div>
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<div class="metric-spread">
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<span>${core.load_avg[0].toFixed(2)}</span>
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<span>${core.load_avg[1].toFixed(2)}</span>
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<span>${core.load_avg[2].toFixed(2)}</span>
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</div>
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</div>` : ""}
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${renderMetric("Core0 Util", (core.core0_util || 0) + " %")}
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${renderMetric("Queue", String(core.queue_len ?? 0))}
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${renderMetric("Errors", String(core.errors ?? 0))}
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</div>
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@@ -1779,7 +1770,7 @@ const char kWebPanelAppHtml[] PROGMEM = R"HTML(
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const kTrendFmt = {
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battery: [v => Math.round(v), "mV"],
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voltage: [v => (v/100).toFixed(2), "V"],
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cpu_load: [v => Math.round(v), "%"],
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core0_util: [v => v, "%"],
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memory: [v => formatBytes(v), ""],
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packets: [v => Math.round(v), "pkts"],
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error_rate: [v => (v/10).toFixed(1), "%"],
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@@ -1827,7 +1818,7 @@ const char kWebPanelAppHtml[] PROGMEM = R"HTML(
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if (recent >= 750) return "#d7a531"; // high
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return "#2f8f4e"; // normal
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}
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if (key === "cpu_load") return "#e07b39";
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if (key === "core0_util") return "#e07b39";
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if (key === "error_rate") return "#ef4444";
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if (key === "gps_satellites") return "#2f8f4e";
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if (key === "signal") return "#3b82f6";
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@@ -1847,7 +1838,7 @@ const char kWebPanelAppHtml[] PROGMEM = R"HTML(
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return baseColor || "#2f8f4e";
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}
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function sparkValueRange(key, values) {
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if (key === "cpu_load") {
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if (key === "core0_util") {
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return { min: 0, max: Math.max(10, ...values) };
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}
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if (key === "packets" || key === "gps_satellites") {
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@@ -2110,7 +2101,7 @@ const char kWebPanelAppHtml[] PROGMEM = R"HTML(
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const sensors = summaryPayload && summaryPayload.sensors ? summaryPayload.sensors : null;
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const gpsEnabled = !!(sensors && sensors.gps_enabled === true);
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const mcuTempPresent = !!(sensors && Number.isFinite(sensors.mcu_temp_c));
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const order = ["battery", "cpu_load", "memory", "packets", "error_rate", "signal", "noise_floor"];
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const order = ["battery", "core0_util", "memory", "packets", "error_rate", "signal", "noise_floor"];
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if (mcuTempPresent) {
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order.splice(1, 0, "mcu_temp");
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}
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