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Trim task stacks and buffers by measurement: +15 KB with IRC up

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Peak stack use was measured through each task's worst case (an
ECDSA-checked install over Wi-Fi and from SD, get/put, a core dump
fetch, an IRC TLS handshake); stacks are now peak plus about 2 KB: loop
8 -> 6 KB, update 8 -> 5, storage 10 -> 6, irc 8 -> 6. The Debug Build's
console ring goes 6 -> 4 KB, serial TX 2 -> 1 KB, the GNSS UART buffer
1 KB -> 512 B.

On the device, with IRC on TLS: 46 KB free (was 31), an 18 KB low (was
9.4). The re-run of every worst case left at least 1.6 KB of stack free
in each task.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT
This commit is contained in:
twisla
2026-10-04 23:02:35 +02:00
co-authored by Claude Opus 5.5
parent 578a39d3c1
commit db265fb757
9 changed files with 14 additions and 11 deletions
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docs/milestones/M2.md
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@@ -1,12 +1,12 @@
# M2 — GNSS
**Status:** steps 1–6 done on the device (branch `m2`). Open: the heap floor (below).
**Status:** steps 1–6 done on the device (branch `m2`). Open: the heap floor during a TLS handshake (below).
## Measured
- **Cold start** (`$PCAS10,2`) to a 3D Fix, by a window: **73 s**, 5 satellites used of 8 in view. A restart of the ESP32 alone keeps the receiver's Fix (the Cap stays powered).
- By a window: 3D Fix from GPS, GLONASS, Galileo and BeiDou, up to 14 of 17 satellites used, HDOP 1.0–1.3.
- **Heap, Debug Build, GNSS on:** 82 KB free with Wi-Fi up; with IRC on TLS, **33 KB free and a 12.6 KB low** during the handshake. The floor is 40 KB, and v0.2.1 (before OTA) measured a 79 KB low. Not a GNSS cost: the OTA and Debug Build work added the `update` (8 KB) and `debug` (6 KB) task stacks, the 6 KB console ring, a larger `storage` stack (10 KB, for SD signature checks), 4 KB of serial buffers, mDNS and two TCP servers. To decide before M2 closes.
- **Heap, Debug Build, GNSS on:** with IRC on TLS, first 33 KB free and a 12.6 KB low (floor 40 KB; v0.2.1 had a 79 KB low). Not a GNSS cost: the OTA and Debug Build work added task stacks, a console ring, serial buffers, mDNS and two TCP servers. **Trimmed by measurement:** each task's peak stack was measured through its worst case (an ECDSA-checked install over Wi-Fi and from SD, get/put, a core dump fetch, an IRC TLS handshake), then stacks were set to peak plus about 2 KB: loop 8→6 KB, update 8→5, storage 10→6, irc 8→6; the console ring 6→4 KB, serial TX 2→1 KB, GNSS UART 1 KB→512 B. **After:** 46 KB free with IRC connected, an 18 KB low. The steady state clears the floor; the TLS handshake peak doesn't yet. Next candidates: mbedTLS dynamic buffers (custom sdkconfig), one network task for the update and debug listeners, mDNS on demand.
**Goal:** the device knows where it is and what time it is without a network: a GNSS Service in the background, a GNSS App with the position and a sky view of the satellites, the clock set from satellites when there's no NTP, and Tracks recorded to the SD card.