Minimal footprint

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Overview

This sample provides an empty main() and various configuration files that can be used to measure Zephyr’s minimal ROM footprint in different configurations.

The following configuration files are available:

  • mt.conf: Enable multithreading

  • no-mt.conf: Disable multithreading

  • no-preempt.conf: Disable preemption

  • no-timers.conf: Disable timers

  • arm.conf: Arm-specific disabling of features

Building and measuring ROM size

The following combinations are suggested for comparing ROM sizes in different configurations. They all target the reel board (Arm Aarch32 architecture).

  • Multithreading enabled

    • Reference ROM size: 7-8KB

    west build -b reel_board -d build/reel_board/mt samples/basic/minimal -- -DCONF_FILE="common.conf mt.conf arm.conf"
    west build -t rom_report -d build/reel_board/mt
    
  • Multithreading enabled, no preemption

    • Reference ROM size: 7-8KB

    west build -b reel_board -d build/reel_board/mt-no-preempt samples/basic/minimal -- -DCONF_FILE="common.conf mt.conf no-preempt.conf arm.conf"
    west build -t rom_report -d build/reel_board/mt-no-preempt
    
  • Multithreading enabled, no preemption, timers disabled

    • Reference ROM size: 3-4KB

    west build -b reel_board -d build/reel_board/mt-no-preempt-no-timers samples/basic/minimal -- -DCONF_FILE="common.conf mt.conf no-preempt.conf no-timers.conf arm.conf"
    west build -t rom_report -d build/reel_board/mt-no-preempt-no-timers
    
  • Multithreading disabled, timers enabled

    • Reference ROM size: 4-5KB

    west build -b reel_board -d build/reel_board/no-mt samples/basic/minimal -- -DCONF_FILE="common.conf no-mt.conf arm.conf"
    west build -t rom_report -d build/reel_board/no-mt
    
  • Multithreading disabled, timers disabled

    • Reference ROM size: 2-3KB

    west build -b reel_board -d build/reel_board/no-mt-no-timers samples/basic/minimal -- -DCONF_FILE="common.conf no-mt.conf no-timers.conf arm.conf"
    west build -t rom_report -d build/reel_board/no-mt-no-timers