Zephyr/NCS too large memory footprint

[icedfluid]

Hi dear forum members,

I’m working on a firmware project for the NRF52840 that utilizes BLE, DFU, I2C, WDT, some cryptographic libraries, and a few sensor libraries. However, despite having 1MB of flash memory, I’m hitting the limits of this configuration, because my flash is separated for DFU. 

Flash organization (very simplified, in fact I have less memory in slot1 and 2)

Coming from a bare-metal development background, where 1MB is considered a substantial amount of memory, this feels quite unusual to me.
My own code occupies less than 8% of the total build, meaning over 92% of the memory footprint comes from Zephyr/NCS.
In my honest opinion, that’s pretty astonishing.

Look, NCS  2.6.2 is taking 135Kb of flash, whouah ! 

Is there a way to reduce this ? 




My project conf file

###############################################################################
# Project Config for running on nrf52840 
###############################################################################
#


# ***IMPORTANT*** => disable these for PRODUCTION
CONFIG_SERIAL=n
CONFIG_LOG=n
CONFIG_BOOT_BANNER=n


#
# Firmware config
#
CONFIG_FIRMWARE_PRODUCTION=y
CONFIG_INSOLE_SIDE_RIGHT=y
CONFIG_TEMPERATURE_SENSORS_CONNECTED=y
CONFIG_I2C_POWER_PIN=y
CONFIG_ACCELEROMETER_CONNECTED=y
CONFIG_ACCELEROMETER_PEDOMETER_ENABLE=n
CONFIG_BATTERY_VOLTAGE_SENSING=y
CONFIG_REBOOT=y
CONFIG_HWINFO=y


#
# Watchdog
#
CONFIG_WATCHDOG=y
CONFIG_WDT_DISABLE_AT_BOOT=y
CONFIG_WATCHDOG_PERIOD=10000


#
# Uart/Serial Terminal
#
CONFIG_WANT_UART=y
CONFIG_WANT_UART_POWER_CTRL=n
CONFIG_LOG_COMMAND_IO=n


#
# BLUETOOTH Connection Monitoring
#
CONFIG_BLE_CONNECTION_MONITORING=y
CONFIG_BLE_CONNECTION_MONITORING_INTERVAL=250
CONFIG_BLE_CONNECTION_MONITORING_COMMAND_TIMEOUT=10000
CONFIG_BLE_CONNECTION_MONITORING_REBOOT_TIMEOUT=2000
CONFIG_BLE_CONNECTION_MONITORING_DFU_TIMEOUT=20000


#
# FOTA
#
CONFIG_PARTITION_MANAGER_ENABLED=y
CONFIG_BOOTLOADER_MCUBOOT=y
CONFIG_NCS_SAMPLE_MCUMGR_BT_OTA_DFU=y
CONFIG_NCS_SAMPLE_MCUMGR_BT_OTA_DFU_SPEEDUP=y

CONFIG_BT_CTLR_DATA_LENGTH_MAX=247
CONFIG_MCUMGR_TRANSPORT_BT_REASSEMBLY=y
CONFIG_MCUMGR_TRANSPORT_NETBUF_SIZE=2475

CONFIG_MCUMGR_MGMT_NOTIFICATION_HOOKS=y
CONFIG_MCUMGR_SMP_COMMAND_STATUS_HOOKS=y
CONFIG_MCUMGR_GRP_IMG_UPLOAD_CHECK_HOOK=y
CONFIG_MCUMGR_GRP_IMG_STATUS_HOOKS=y



#
# Debugging Tasks
#
CONFIG_WANT_ALLPURPOSE_GPIO=n


#
# CONFIG CPP / LIBC
#
CONFIG_CPP=y
CONFIG_REQUIRES_FULL_LIBCPP=y # Because we use map and set, we must require FULL libc
#CONFIG_GLIBCXX_LIBCPP=y
#CONFIG_MINIMAL_LIBCPP=y
CONFIG_CBPRINTF_FP_SUPPORT=y
CONFIG_CBPRINTF_N_SPECIFIER=y
CONFIG_CBPRINTF_FULL_INTEGRAL=y


#
# STACK
#
CONFIG_MAIN_STACK_SIZE=3584
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=5120
#CONFIG_THREAD_ANALYZER=y
#CONFIG_THREAD_ANALYZER_AUTO_STACK_SIZE=2048
#CONFIG_THREAD_ANALYZER_AUTO=y
#CONFIG_THREAD_ANALYZER_AUTO_INTERVAL=30
#CONFIG_THREAD_ANALYZER_USE_LOG=y


#
# Power Management
#
CONFIG_POWEROFF=y
CONFIG_PM_DEVICE=y
# https://devzone.nordicsemi.com/f/nordic-q-a/103764/getting-low-power-consumption-with-external-sensors
CONFIG_PM_DEVICE_RUNTIME=y


#
# DEBUGGING
#
CONFIG_DEBUG_OPTIMIZATIONS=n  #CONFIG_DEBUG_OPTIMIZATIONS=y leads to crash the thread creation in qemu_x86
CONFIG_DEBUG_THREAD_INFO=n
CONFIG_EXCEPTION_STACK_TRACE=n
CONFIG_DEBUG_INFO=y
CONFIG_DEBUG_COREDUMP=n


#
# CONSOLE (enable the Terminal)
#
CONFIG_UART_USE_RUNTIME_CONFIGURE=y
CONFIG_CONSOLE=y
CONFIG_UART_CONSOLE=y
CONFIG_CONSOLE_SUBSYS=y
CONFIG_CONSOLE_GETLINE=y
CONFIG_CONSOLE_INPUT_MAX_LINE_LEN=100


#
# LOGGING
#
#CONFIG_LOG=n
#CONFIG_LOG_OVERRIDE_LEVEL=3
CONFIG_LOG_DEFAULT_LEVEL=3
CONFIG_LOG_MODE_DEFERRED=y
#CONFIG_LOG_RUNTIME_FILTERING=n
CONFIG_LOG_BUFFER_SIZE=2048
CONFIG_LOG_PRINTK=y
#CONFIG_LOG_PROCESS_TRIGGER_THRESHOLD=0
#CONFIG_COVERAGE=n
#CONFIG_LOG_TAG_MAX_LEN=8

##### RTT SEGGER LOG ####

#CONFIG_LOG_MODE_IMMEDIATE=n
CONFIG_LOG_BACKEND_RTT=n
#CONFIG_USE_SEGGER_RTT=y
#CONFIG_RTT_CONSOLE=y
#CONFIG_LOG_BACKEND_UART=n
#CONFIG_UART_CONSOLE=n
#CONFIG_LOG_BACKEND_RTT_MESSAGE_SIZE=32

##### UART LOG ####
CONFIG_LOG_BACKEND_UART=y


#
# BLUETOOTH
#
CONFIG_BT=y
CONFIG_BT_PERIPHERAL=y
CONFIG_BT_DEVICE_NAME_DYNAMIC=y
CONFIG_BT_DEVICE_NAME_MAX=16
#768 = Thermometer
CONFIG_BT_DEVICE_APPEARANCE=768
CONFIG_BT_MAX_CONN=1
CONFIG_BT_MAX_PAIRED=1
CONFIG_BT_NUS=y
CONFIG_BT_L2CAP_TX_MTU=247
CONFIG_BT_BUF_ACL_TX_COUNT=3
CONFIG_BT_BUF_ACL_TX_SIZE=247
#this one control the MTU for sending (yes, it's strange, RX ?!)
CONFIG_BT_BUF_ACL_RX_SIZE=247
#tx power stuff
CONFIG_BT_CTLR_TX_PWR_0=y
CONFIG_BT_CTLR_TX_PWR_DYNAMIC_CONTROL=y


#
# I2C
#
CONFIG_I2C=y
CONFIG_I2C_LOG_LEVEL_OFF=y
CONFIG_I2C_DUMP_MESSAGES=n


#
# ADC
#
CONFIG_ADC=y


#
# LittleFS / Flash
#
CONFIG_LITTLEFS_USE_FLASH=y
CONFIG_LITTLEFS_WIPE_AT_BOOT=n
CONFIG_FLASH=y
CONFIG_FLASH_MAP=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_FILE_SYSTEM=y
CONFIG_FILE_SYSTEM_LITTLEFS=y
CONFIG_FILE_SYSTEM_MAX_FILE_NAME=16
#CONFIG_FS_LITTLEFS_NUM_DIRS=1


#
# Assert
#
CONFIG_ASSERT=y


#
# CRC
#
CONFIG_CRC=y


#
# BASE64
#
CONFIG_BASE64=y


#
# Crypto
#
CONFIG_CRYPTO=y
CONFIG_CRYPTO_MBEDTLS_SHIM=y
CONFIG_MBEDTLS_CIPHER_CCM_ENABLED=y
CONFIG_CRYPTO_LOG_LEVEL_OFF=y


#
# RAM power down
#
CONFIG_RAM_POWER_DOWN_LIBRARY=y

Thank you very much.

Vincent

[Sigurd]

Hi!

I recommend having a look at this guide on Memory footprint optimization:

https://docs.nordicsemi.com/bundle/ncs-2.6.2/page/nrf/test_and_optimize/optimizing/memory.html

Also, as mentioned in the guide, for reference, you can find minimal footprint configurations of the Bluetooth: Peripheral LBS sample in nrf/samples/bluetooth/peripheral_lbs/prj_minimal.conf

https://github.com/nrfconnect/sdk-nrf/blob/v2.6.2/samples/bluetooth/peripheral_lbs/prj_minimal.conf

[icedfluid]

Hi Sigurd 

I’ve already tried many options from prj_minimal.conf. The most recent ones I tested reduced the footprint by only a few hundred bytes. Unfortunately, that’s not a significant improvement and, in my opinion, clearly not enough.

Even with all printk and logs disabled, the full firmware archive occupies 86% of a single flash slot. With debug logs enabled, it jumps to 96%.

Is there really no way to achieve a substantial reduction in the footprint of Zephyr/NCS and the libraries used during the build process?

[Sigurd]

icedfluid said:

Is there really no way to achieve a substantial reduction in the footprint of Zephyr/NCS and the libraries used during the build process?

Depends on your application. Use e.g. the Memory report UI to identity what is taking a lot of flash. https://docs.nordicsemi.com/bundle/nrf-connect-vscode/page/reference/ui_memory_report.html , Also, e.g. the "No paths" at 120.12 kB should be investigated to see if there is something there you can reduce.