[esp32] Document heap_in_iram advanced option #5851
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Pull request overview
Adds documentation for the heap_in_iram advanced option in ESP32 IDF framework configuration. This option controls whether heap allocation functions are kept in IRAM or moved to flash memory, with the default placing them in flash to save 4-6 KB of IRAM.
- Documents the new
heap_in_iramboolean option under FreeRTOS Memory Options - Explains the tradeoff between IRAM savings and heap operation performance
- Provides guidance on when users might need to enable this option
swoboda1337
approved these changes
Jan 5, 2026
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Description:
Add documentation for the new
heap_in_iramadvanced option in the ESP32 IDF framework configuration.This option allows users to keep heap functions (malloc, free, realloc) in IRAM instead of the new default behavior of placing them in flash. The default (flash) saves ~4-6 KB of IRAM, which is the payoff from months of work reducing heap churn throughout the codebase.
Related issue (if applicable): n/a
Pull request in esphome with YAML changes (if applicable):
Checklist:
I am merging into
nextbecause this is new documentation that has a matching pull-request in esphome as linked above.or
I am merging into
currentbecause this is a fix, change and/or adjustment in the current documentation and is not for a new component or feature.Link added in
/components/_index.mdwhen creating new documents for new components or cookbook.