ESP32: 1.26 preview, MICROPY_ROM_TEXT_COMPRESSION and large increase of micropython.bin size with ulab

[ricksorensen]

Using the latest release (30 Apr 2025) when I compiled an ESP32S3 with ulab the size of micropython.bin exceeded significantly the app partition size. This changed after 1.25.0 release. I do not understand what the MICROPY_ROM_TEXT_COMPRESSION parameter does.

The size of micropython.bin increase by 1_300_160 bytes (about 70%) and the size of micropython.elf increased by 4_714_700 bytes. If I build without USER_C_MODULES there is not a significant increase in size. If I include significantly smaller/simpler USER_C_MODULES I did not notice a large size change. This happens with both the GENER)C_S3 and GENERIC_C3 builds, I do not know if it is micropython or ulab code that is impacted.

# the current release
ls -l buildmaster/firmware* buildmaster/micropython.*
ls: cannot access 'buildmaster/firmware*': No such file or directory
-rw-rw-r-- 1 rick rick  3147312 Apr 30 09:43  buildmaster/micropython.bin
-rwxrwxr-x 1 rick rick 25419540 Apr 30 09:43  buildmaster/micropython.elf
-rw-rw-r-- 1 rick rick 11662086 Apr 30 09:43  buildmaster/micropython.map
# the current release, modifed esp32_common.cmake 
# removed TEXT_COMPRESSION define, added messages
$ ls -l build25/firmware* build25/micropython.*
-rw-rw-r-- 1 rick rick  1912688 Apr 30 09:45 build25/firmware.bin
-rw-rw-r-- 1 rick rick  1847152 Apr 30 09:45 build25/micropython.bin
-rwxrwxr-x 1 rick rick 20704840 Apr 30 09:45 build25/micropython.elf
-rw-rw-r-- 1 rick rick 11661237 Apr 30 09:45 build25/micropython.map
-rw-rw-r-- 1 rick rick  3694592 Apr 30 09:45 build25/micropython.uf2

The diff of the modified cmake file is:

$ git diff ports/esp32/esp32_common.cmake
diff --git a/ports/esp32/esp32_common.cmake b/ports/esp32/esp32_common.cmake
index c54f5a540..e96d921df 100644
--- a/ports/esp32/esp32_common.cmake
+++ b/ports/esp32/esp32_common.cmake
@@ -28,11 +28,6 @@ if(NOT DEFINED MICROPY_PY_TINYUSB)
     endif()
 endif()
 
-# Enable error text compression by default.
-if(NOT MICROPY_ROM_TEXT_COMPRESSION)
-    set(MICROPY_ROM_TEXT_COMPRESSION ON)
-endif()
-
 # Include core source components.
 include(${MICROPY_DIR}/py/py.cmake)
 
@@ -43,6 +38,7 @@ if(NOT CMAKE_BUILD_EARLY_EXPANSION)
     # Enable extmod components that will be configured by extmod.cmake.
     # A board may also have enabled additional components.
     if (NOT DEFINED MICROPY_PY_BTREE)
+        message(STATUS "BTREE ON")
         set(MICROPY_PY_BTREE ON)
     endif()
 
@@ -279,6 +275,7 @@ target_include_directories(${MICROPY_TARGET} PUBLIC
 
 # Add additional extmod and usermod components.
 if (MICROPY_PY_BTREE)
+    message(STATUS "BTREE libraries linked")
     target_link_libraries(${MICROPY_TARGET} micropy_extmod_btree)
 endif()
 target_link_libraries(${MICROPY_TARGET} usermod)

[ricksorensen]

not resolved. Seems to be resolved by 20250513. updates to py/mkrules.cmake
Current 1.26.preview build still show large micropython.bin growth when compiling with ulab, while v1.25 builds okay.

Using IDF 5.4.1 and compiling for ESP32_GENERIC_S3 board with SPIRAM_OCT variant
Pulling micropython with commit id: master: 49f81d5046aaeb31f90626426363ae2518dbd810
Pulled latest ulab repo into $MYDIR/ulab

Build command (just pulled latest ulab repo into $MYDIR/ulab

make -j 1 BOARD=ESP32_GENERIC_S3 BOARD_VARIANT=SPIRAM_OCT USER_C_MODULES=$MYDIR/ulab/code/micropython.cmake

Two runs. First set MICROPY_ROM_TEXT_COMPRESSION ON in esp32_common.cmake which is default. The second set MICROPY_ROM_TEXT_COMPRESSION ON in modified esp32_common.cmake. Size results:

compression  micropython.bin  firmware.bin
ON                   3178576  over size
OFF                  1882240  1947776

Without ulab there is a noticeable decrease (few thousand bytes) in image size using compression. Results are similar for both S3 and C3. I wondered if the number of symbols in the external ulab module created a problem, or if the ulab code needs to be updated for v1.26.