How to reduce DRAM usage or shift data from DRAM to IRAM/Flash on ESP32C3 (in Zephyr 4.2)

[pawankumar0099]

Hi everyone,

I’m working on an ESP32C3 target, and I’m hitting a memory bottleneck where the DRAM region is almost full while other segments still have room.
Here’s the memory usage summary:

As you can see, dram0_0_seg is nearly full (99.58%), while IRAM and Flash still have plenty of space.

I’d like to ask:

Is it possible to reduce DRAM usage or move certain variables or buffers to IRAM or Flash in Zephyr?

Are there known Kconfig options, compiler/linker flags, or best practices to optimize memory layout for ESP32C3 in Zephyr?

I’ve already verified that many global/static buffers are taking space in DRAM, and I’m looking for efficient ways to offload them.

Thanks in advance for any guidance or optimization tips

[rftafas]

IRAM and DRAM are the same memory on different addresses. PTAL: https://developer.espressif.com/blog/2024/08/esp32-memory-map-101/

You can use the RTC_RAM for extra memory.
Also, the latest revision of ESP32-C3 has more RAM available due to optimizations on ROM code.

[sylvioalves]

@pawankumar0099 you could change heap pool size, net stack and ble buffers if using it. The same with mbedtls and so. Have you tried that?

[pawankumar0099]

@sylvioalves Yes, I have tried that. Things stop working if I reduce the heap pool size.
To establish a TLS connection, I’m using a minimum heap size of CONFIG_MBEDTLS_HEAP_SIZE=40000.
BLE also uses heap memory, which I can’t configure (CONFIG_HEAP_MEM_POOL_ADD_SIZE_ESP_BT=25600).

In my use case, BLE is only used to share Wi-Fi credentials. So, is it possible for BLE to use the same heap that’s allocated for mbedTLS?