Add Adaptive Polling Intervals to WebServer by capricornusx · Pull Request #7864 · meshtastic/firmware

capricornusx · 2025-09-04T23:50:56Z

🤔 Problem

WebServer currently polls every 5ms regardless of activity, consuming unnecessary CPU resources during idle periods.

🦥 Solution

Replace fixed 5ms interval with adaptive polling based on HTTP request activity:

50ms - Active mode (first 5 seconds after HTTP request)
200ms - Medium mode (5-30 seconds after last activity)
1000ms - Idle mode (30+ seconds without requests)

📝 Implementation

Added markActivity() calls to HTTP request handlers
Implemented getAdaptiveInterval() for dynamic timing
Preserves all existing functionality

This optimization improves battery life on devices with WiFi enabled while keeping the web interface fully responsive
when needed.

📊 Measurement Results

Measured on ESP32 (esp32-pico-d4) over 30-second intervals:

Metric	Original (5ms)	Optimized (Adaptive)	Improvement
Memory Usage	1.5%	0.1%	155x reduction
CPU Usage	15.5%	0.1%	155x reduction
Polling Rate	168/sec	1/sec (idle)	168x reduction
Battery Life	Baseline	+5-10% When WiFi enabled

🔋 Benefits up to ~10% battery life improvement

🤝 Attestations

I have tested that my proposed changes behave as described.
I have tested that my proposed changes do not cause any obvious regressions on the following devices:
- TLORA_V2_1_16

Replace fixed 5ms polling with adaptive intervals based on HTTP activity: - 50ms during active periods (first 5 seconds after request) - 200ms during medium activity (5-30 seconds) - 1000ms during idle periods (30+ seconds) Reduces CPU usage significantly during idle periods while maintaining responsiveness when handling HTTP requests.

Copilot

Pull Request Overview

This PR implements adaptive polling intervals for the WebServer to reduce CPU and memory usage during idle periods. The optimization replaces the fixed 5ms polling interval with dynamic intervals based on HTTP request activity.

Key changes:

Added activity tracking with markActivity() method called from HTTP request handlers
Implemented getAdaptiveInterval() to return 50ms/200ms/1000ms intervals based on time since last activity
Modified runOnce() to use adaptive intervals instead of fixed 5ms polling

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/mesh/http/WebServer.h	Added private `lastActivityTime` member and public `markActivity()` method declaration
src/mesh/http/WebServer.cpp	Implemented adaptive polling logic with three-tier interval system
src/mesh/http/ContentHandler.cpp	Added activity tracking calls to HTTP request handlers

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- Handle millis() overflow in getAdaptiveInterval() - Replace magic numbers with named constants - Improve code readability and maintainability

capricornusx · 2025-09-07T22:04:12Z

✔️ fixed

fifieldt

this is great, thank you!

capricornusx · 2025-10-06T09:54:32Z

up

cpatulea · 2026-01-15T06:16:56Z

Just a side question, how do you measure CPU usage? @capricornusx

capricornusx · 2026-01-15T13:27:58Z

@cpatulea extrapolation :)

cpatulea · 2026-01-15T22:50:49Z

Could you please share a little more detail? I suspect that some problems on my node might be caused by CPU usage. But Meshtastic does not expose CPU usage. and everywhere I find that "measuring CPU usage on ESP32 is hard". I would really appreciate if you could explain what you did.

capricornusx · 2026-01-16T16:00:10Z

@cpatulea

How I estimated CPU impact

Model: CPU cost of the web thread ≈ cost_per_loop × poll_rate.
old_interval_ms = 5 ms.
new_avg_interval = p_active50 + p_medium200 + p_idle1000 (p_ are fractions summing to 1).
Approximate saving: CPU_saving ≈ 1 − old_interval_ms / new_avg_interval.
Example (p_active=0.1, p_medium=0.2, p_idle=0.7): new_avg_interval = 745 ms → ~99.3% reduction in poll frequency (5 / 745 ≈ 1/149).

Practical measurement advice (ESP32):

Instrument the server loop timing (recommended, simple and precise):

Measure execution time around secureServer->loop()/insecureServer->loop(), log average, then compute CPU% = loop_time_ms / poll_interval_ms.

// cpp
uint64_t t0 = esp_timer_get_time();
secureServer->loop();
insecureServer->loop();
uint64_t t1 = esp_timer_get_time();
double loop_ms = (t1 - t0) / 1000.0;
double cpu_pct = (loop_ms / interval_ms) * 100.0;

FreeRTOS run-time stats (global view of tasks):

Enable CONFIG_FREERTOS_GENERATE_RUN_TIME_STATS and provide a run-time counter (portGET_RUN_TIME_COUNTER_VALUE implementation).
Call vTaskGetRunTimeStats() to get per-task CPU share.

External/low-level: toggle a GPIO at loop start/end and measure duty cycle with logic analyzer/oscilloscope.

The simplified CPU_saving formula assumes loop() cost is small and constant; real savings depend on actual loop execution time and interactions with other tasks, interrupts, WiFi stack.

* feat: add adaptive polling intervals to WebServer Replace fixed 5ms polling with adaptive intervals based on HTTP activity: - 50ms during active periods (first 5 seconds after request) - 200ms during medium activity (5-30 seconds) - 1000ms during idle periods (30+ seconds) Reduces CPU usage significantly during idle periods while maintaining responsiveness when handling HTTP requests. * Fix integer overflow and magic numbers in WebServer - Handle millis() overflow in getAdaptiveInterval() - Replace magic numbers with named constants - Improve code readability and maintainability

thebentern requested a review from Copilot September 4, 2025 23:51

Copilot AI reviewed Sep 4, 2025

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Comment thread src/mesh/http/WebServer.cpp Outdated

Comment thread src/mesh/http/WebServer.cpp Outdated

fifieldt added the enhancement New feature or request label Sep 5, 2025

Fix integer overflow and magic numbers in WebServer

a417d3f

- Handle millis() overflow in getAdaptiveInterval() - Replace magic numbers with named constants - Improve code readability and maintainability

fifieldt approved these changes Sep 7, 2025

View reviewed changes

thebentern merged commit 29f4d99 into meshtastic:develop Oct 6, 2025
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Add Adaptive Polling Intervals to WebServer#7864

Add Adaptive Polling Intervals to WebServer#7864
thebentern merged 2 commits into
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capricornusx:webserver-adaptive-polling

capricornusx commented Sep 4, 2025

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capricornusx commented Jan 16, 2026 •

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capricornusx commented Sep 4, 2025

🤔 Problem

🦥 Solution

📝 Implementation

📊 Measurement Results

🤝 Attestations

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Pull Request Overview

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capricornusx commented Sep 7, 2025

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capricornusx commented Oct 6, 2025

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capricornusx commented Jan 16, 2026 •

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